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  • DDD and MVC: Difference between 'Model' and 'Entity'

    - by Nathan Loding
    I'm seriously confused about the concept of the 'Model' in MVC. Most frameworks that exist today put the Model between the Controller and the database, and the Model almost acts like a database abstraction layer. The concept of 'Fat Model Skinny Controller' is lost as the Controller starts doing more and more logic. In DDD, there is also the concept of a Domain Entity, which has a unique identity to it. As I understand it, a user is a good example of an Entity (unique userid, for instance). The Entity has a life-cycle -- it's values can change throughout the course of the action -- and then it's saved or discarded. The Entity I describe above is what I thought Model was supposed to be in MVC? How off-base am I? To clutter things more, you throw in other patterns, such as the Repository pattern (maybe putting a Service in there). It's pretty clear how the Repository would interact with an Entity -- how does it with a Model? Controllers can have multiple Models, which makes it seem like a Model is less a "database table" than it is a unique Entity. So, in very rough terms, which is better? No "Model" really ... class MyController { public function index() { $repo = new PostRepository(); $posts = $repo->findAllByDateRange('within 30 days'); foreach($posts as $post) { echo $post->Author; } } } Or this, which has a Model as the DAO? class MyController { public function index() { $model = new PostModel(); // maybe this returns a PostRepository? $posts = $model->findAllByDateRange('within 30 days'); while($posts->getNext()) { echo $posts->Post->Author; } } } Both those examples didn't even do what I was describing above. I'm clearly lost. Any input?

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  • Synonym for "Many-to-Many" relationship (relational databases)

    - by Byron
    What's a synonym for a "many-to-many" relationship? I've finished writing an object-relational mapper but I'm still stumped as to what to name the function that adds that relation. addParent() and addChild() seemed quite logical for the many-to-one/one-to-many and addSuperclass() for one-to-one inheritance, but addManyToMany() would sound quite unintuitive to an object-oriented programmer. addSibling() or addCousin() doesn't really make sense either. Any suggestions? And before you dismiss this as a non-programming question, please remember that consistent naming schemes and encapsulation are pretty integral to programming :)

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  • CSS and Page Size and Horizontal Scrollbar

    - by Steve
    When I added some CSS stuff to my page, the page got wider and and horizontal appeared even the content is very minimal and does not require to scroll. How can I remove it. I used the following to remove it but it appears as a hack and I am just playing around with CSS, so is there a proper way to do this

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  • Asp.NET custom templated datalist throws argument out of range (index) on button press

    - by MrTortoise
    I have a class BaseTemplate public abstract class BaseTemplate : ITemplate This adds the controls, and provides abstract methods to implement in the inheriting class. The inheriting class then adds its html according to its data source and manages the data binding. This all works fine - I get the control appearing with properly parsed html. The problem is that the base class adds controls into the template that have their own CommandName arguments; the idea is that the class that implements the custom templated dataList will provide the logic of setting the Selected and Edit Indexes. This class also manages the data binding, etc. It sets all of the templates on the datalist in the Init method (which was another cause of this exception). The exception gets thrown when I hit one of these buttons - I have tried hooking up both their click and command events everywhere in case this was the problem. I have also ensured that their command names do not match any of the system ones. The stack trace does not include any references to my methods or objects which is why I am so stuck. It is the most unhelpful message I can imagine. The really frustrating thing is that I cannot get a breakpoint to fire - i.e. the problem is happening after I click the button, but before and of my code can execute. The last time this exception happened was when I had this code in a user control and was assigning the templates to the datalist in the PageLoad. I moved these into init to fix that problem; however, this is a problem that was there then and I have no idea what is causing it let alone how to solve it (and index out of range doesn't really help without knowing what index.) The Exception Details Exception Details: System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: index The Stack Trace: [ArgumentOutOfRangeException: Specified argument was out of the range of valid values. Parameter name: index] System.Web.UI.ControlCollection.get_Item(Int32 index) +8665582 System.Web.UI.WebControls.DataList.GetItem(ListItemType itemType, Int32 repeatIndex) +8667655 System.Web.UI.WebControls.DataList.System.Web.UI.WebControls.IRepeatInfoUser.GetItemStyle(ListItemType itemType, Int32 repeatIndex) +11 System.Web.UI.WebControls.RepeatInfo.RenderVerticalRepeater(HtmlTextWriter writer, IRepeatInfoUser user, Style controlStyle, WebControl baseControl) +8640873 System.Web.UI.WebControls.RepeatInfo.RenderRepeater(HtmlTextWriter writer, IRepeatInfoUser user, Style controlStyle, WebControl baseControl) +27 System.Web.UI.WebControls.DataList.RenderContents(HtmlTextWriter writer) +208 System.Web.UI.WebControls.BaseDataList.Render(HtmlTextWriter writer) +30 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +163 System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +32 System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +51 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +40 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19 System.Web.UI.Page.Render(HtmlTextWriter writer) +29 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1266 The code Base class: public abstract class BaseTemplate : ITemplate { ListItemType _templateType; public BaseTemplate(ListItemType theTemplateType) { _templateType = theTemplateType; } public ListItemType ListItemType { get { return _templateType; } } #region ITemplate Members public void InstantiateIn(Control container) { PlaceHolder ph = new PlaceHolder(); container.Controls.Add(ph); Literal l = new Literal(); switch (_templateType) { case ListItemType.Header: { ph.Controls.Add(new LiteralControl(@"<table><tr>")); InstantiateInHeader(ph); ph.Controls.Add(new LiteralControl(@"</tr>")); break; } case ListItemType.Footer: { ph.Controls.Add(new LiteralControl(@"<tr>")); InstantiateInFooter(ph); ph.Controls.Add(new LiteralControl(@"</tr></table>")); break; } case ListItemType.Item: { ph.Controls.Add(new LiteralControl(@"<tr>")); InstantiateInItem(ph); ph.Controls.Add(new LiteralControl(@"<td>")); Button select = new Button(); select.ID = "btnSelect"; select.CommandName = "SelectRow"; select.Text = "Select"; ph.Controls.Add(select); ph.Controls.Add(new LiteralControl(@"</td>")); ph.Controls.Add(new LiteralControl(@"</tr>")); ph.DataBinding += new EventHandler(ph_DataBinding); break; } case ListItemType.AlternatingItem: { ph.Controls.Add(new LiteralControl(@"<tr>")); InstantiateInAlternatingItem(ph); ph.Controls.Add(new LiteralControl(@"<td>")); Button select = new Button(); select.ID = "btnSelect"; select.CommandName = "SelectRow"; select.Text = "Select"; ph.Controls.Add(select); ph.Controls.Add(new LiteralControl(@"</td>")); ph.Controls.Add(new LiteralControl(@"</tr>")); ph.DataBinding+=new EventHandler(ph_DataBinding); break; } case ListItemType.SelectedItem: { ph.Controls.Add(new LiteralControl(@"<tr>")); InstantiateInItem(ph); ph.Controls.Add(new LiteralControl(@"<td>")); Button edit = new Button(); edit.ID = "btnEdit"; edit.CommandName = "EditRow"; edit.Text = "Edit"; ph.Controls.Add(edit); Button delete = new Button(); delete.ID = "btnDelete"; delete.CommandName = "DeleteRow"; delete.Text = "Delete"; ph.Controls.Add(delete); ph.Controls.Add(new LiteralControl(@"</td>")); ph.Controls.Add(new LiteralControl(@"</tr>")); ph.DataBinding += new EventHandler(ph_DataBinding); break; } case ListItemType.EditItem: { ph.Controls.Add(new LiteralControl(@"<tr>")); InstantiateInEdit(ph); ph.Controls.Add(new LiteralControl(@"<td>")); Button save = new Button(); save.ID = "btnSave"; save.CommandName = "SaveRow"; save.Text = "Save"; ph.Controls.Add(save); Button cancel = new Button(); cancel.ID = "btnCancel"; cancel.CommandName = "CancelRow"; cancel.Text = "Cancel"; ph.Controls.Add(cancel); ph.Controls.Add(new LiteralControl(@"</td>")); ph.Controls.Add(new LiteralControl(@"</tr>")); ph.DataBinding += new EventHandler(ph_DataBinding); break; } case ListItemType.Separator: { InstantiateInSeperator(ph); break; } } } void ph_DataBinding(object sender, EventArgs e) { DataBindingOverride(sender, e); } /// <summary> /// the controls placed into the PlaceHolder will get wrapped in &lt;table&gt;&lt;tr&gt; &lt;/tr&gt;. I.e. you need to provide the column names wrapped in &lt;td&gt;&lt;/td&gt; tags. /// </summary> /// <param name="header"></param> public abstract void InstantiateInHeader(PlaceHolder ph); /// <summary> /// the controls will have a column added after them and so require each column to be properly wrapped in &lt;td&gt;&lt;/td&gt; tags. The &lt;tr&gt;&lt;/tr&gt; is handled in the base class. /// </summary> /// <param name="ph"></param> public abstract void InstantiateInItem(PlaceHolder ph); /// <summary> /// the controls will have a column added after them and so require each column to be properly wrapped in &lt;td&gt;&lt;/td&gt; tags. The &lt;tr&gt;&lt;/tr&gt; is handled in the base class. /// </summary> /// <param name="ph"></param> public abstract void InstantiateInAlternatingItem(PlaceHolder ph); /// <summary> /// the controls will have a column added after them and so require each column to be properly wrapped in &lt;td&gt;&lt;/td&gt; tags. The &lt;tr&gt;&lt;/tr&gt; is handled in the base class. /// </summary> /// <param name="ph"></param> public abstract void InstantiateInEdit(PlaceHolder ph); /// <summary> /// Any html used in the footer will have &lt;/tr&gt;&lt;table&gt; appended to the end. /// &lt;tr&gt; will be appended to the front. /// </summary> /// <param name="ph"></param> public abstract void InstantiateInFooter(PlaceHolder ph); /// <summary> /// the controls will have a column added after them and so require each column to be properly wrapped in &lt;td&gt;&lt;/td&gt; tags. The &lt;tr&gt;&lt;/tr&gt; is handled in the base class. /// Adds Delete and Edit Buttons after the table contents. /// </summary> /// <param name="ph"></param> public abstract void InstantiateInSelectedItem(PlaceHolder ph); /// <summary> /// The base class provides no &lt;tr&gt;&lt;/tr&gt; tags /// </summary> /// <param name="ph"></param> public abstract void InstantiateInSeperator(PlaceHolder ph); /// <summary> /// Use this method to bind the controls to their data. /// </summary> /// <param name="sender"></param> /// <param name="e"></param> public abstract void DataBindingOverride(object sender, EventArgs e); #endregion } Inheriting class: public class NominalGroupTemplate : BaseTemplate { public NominalGroupTemplate(ListItemType theListItemType) : base(theListItemType) { } public override void InstantiateInHeader(PlaceHolder ph) { ph.Controls.Add(new LiteralControl(@"<td>ID</td><td>Group</td><td>IsPositive</td>")); } public override void InstantiateInItem(PlaceHolder ph) { ph.Controls.Add(new LiteralControl(@"<td>")); Label lblID = new Label(); lblID.ID = "lblID"; ph.Controls.Add(lblID); ph.Controls.Add(new LiteralControl(@"</td><td>")); Label lblGroup = new Label(); lblGroup.ID = "lblGroup"; ph.Controls.Add(lblGroup); ph.Controls.Add(new LiteralControl(@"</td><td>")); CheckBox chkIsPositive = new CheckBox(); chkIsPositive.ID = "chkIsPositive"; chkIsPositive.Enabled = false; ph.Controls.Add(chkIsPositive); ph.Controls.Add(new LiteralControl(@"</td>")); } public override void InstantiateInAlternatingItem(PlaceHolder ph) { InstantiateInItem(ph); } public override void InstantiateInEdit(PlaceHolder ph) { ph.Controls.Add(new LiteralControl(@"<td>")); Label lblID = new Label(); lblID.ID = "lblID"; ph.Controls.Add(lblID); ph.Controls.Add(new LiteralControl(@"</td><td>")); TextBox txtGroup = new TextBox(); txtGroup.ID = "txtGroup"; txtGroup.Visible = true; txtGroup.Enabled = true ; ph.Controls.Add(txtGroup); ph.Controls.Add(new LiteralControl(@"</td><td>")); CheckBox chkIsPositive = new CheckBox(); chkIsPositive.ID = "chkIsPositive"; chkIsPositive.Visible = true; chkIsPositive.Enabled = true ; ph.Controls.Add(chkIsPositive); ph.Controls.Add(new LiteralControl(@"</td>")); } public override void InstantiateInFooter(PlaceHolder ph) { InstantiateInHeader(ph); } public override void InstantiateInSelectedItem(PlaceHolder ph) { ph.Controls.Add(new LiteralControl(@"<td>")); Label lblID = new Label(); lblID.ID = "lblID"; ph.Controls.Add(lblID); ph.Controls.Add(new LiteralControl(@"</td><td>")); TextBox txtGroup = new TextBox(); txtGroup.ID = "txtGroup"; txtGroup.Visible = true; txtGroup.Enabled = false; ph.Controls.Add(txtGroup); ph.Controls.Add(new LiteralControl(@"</td><td>")); CheckBox chkIsPositive = new CheckBox(); chkIsPositive.ID = "chkIsPositive"; chkIsPositive.Visible = true; chkIsPositive.Enabled = false; ph.Controls.Add(chkIsPositive); ph.Controls.Add(new LiteralControl(@"</td>")); } public override void InstantiateInSeperator(PlaceHolder ph) { } public override void DataBindingOverride(object sender, EventArgs e) { PlaceHolder ph = (PlaceHolder)sender; DataListItem li = (DataListItem)ph.NamingContainer; int id = Convert.ToInt32(DataBinder.Eval(li.DataItem, "ID")); string group = (string)DataBinder.Eval(li.DataItem, "Group"); bool isPositive = Convert.ToBoolean(DataBinder.Eval(li.DataItem, "IsPositive")); switch (this.ListItemType) { case ListItemType.Item: case ListItemType.AlternatingItem: { ((Label)ph.FindControl("lblID")).Text = id.ToString(); ((Label)ph.FindControl("lblGroup")).Text = group; ((CheckBox)ph.FindControl("chkIsPositive")).Text = isPositive.ToString(); break; } case ListItemType.EditItem: case ListItemType.SelectedItem: { ((TextBox)ph.FindControl("lblID")).Text = id.ToString(); ((TextBox)ph.FindControl("txtGroup")).Text = group; ((CheckBox)ph.FindControl("chkIsPositive")).Text = isPositive.ToString(); break; } } } } From here I added the control to a page the code behind public partial class NominalGroupbroke : System.Web.UI.UserControl { public void SetNominalGroupList(IList<BONominalGroup> theNominalGroups) { XElement data = Serialiser<BONominalGroup>.SerialiseObjectList(theNominalGroups); ViewState.Add("nominalGroups", data.ToString()); dlNominalGroup.DataSource = theNominalGroups; dlNominalGroup.DataBind(); } protected void Page_init() { dlNominalGroup.HeaderTemplate = new NominalGroupTemplate(ListItemType.Header); dlNominalGroup.ItemTemplate = new NominalGroupTemplate(ListItemType.Item); dlNominalGroup.AlternatingItemTemplate = new NominalGroupTemplate(ListItemType.AlternatingItem); dlNominalGroup.SeparatorTemplate = new NominalGroupTemplate(ListItemType.Separator); dlNominalGroup.SelectedItemTemplate = new NominalGroupTemplate(ListItemType.SelectedItem); dlNominalGroup.EditItemTemplate = new NominalGroupTemplate(ListItemType.EditItem); dlNominalGroup.FooterTemplate = new NominalGroupTemplate(ListItemType.Footer); } protected void Page_Load(object sender, EventArgs e) { dlNominalGroup.ItemCommand += new DataListCommandEventHandler(dlNominalGroup_ItemCommand); } void dlNominalGroup_Init(object sender, EventArgs e) { dlNominalGroup.HeaderTemplate = new NominalGroupTemplate(ListItemType.Header); dlNominalGroup.ItemTemplate = new NominalGroupTemplate(ListItemType.Item); dlNominalGroup.AlternatingItemTemplate = new NominalGroupTemplate(ListItemType.AlternatingItem); dlNominalGroup.SeparatorTemplate = new NominalGroupTemplate(ListItemType.Separator); dlNominalGroup.SelectedItemTemplate = new NominalGroupTemplate(ListItemType.SelectedItem); dlNominalGroup.EditItemTemplate = new NominalGroupTemplate(ListItemType.EditItem); dlNominalGroup.FooterTemplate = new NominalGroupTemplate(ListItemType.Footer); } void dlNominalGroup_DataBinding(object sender, EventArgs e) { } void deleteNominalGroup(int index) { XElement data = XElement.Parse(Convert.ToString( ViewState["nominalGroups"] )); IList<BONominalGroup> list = Serialiser<BONominalGroup>.DeserialiseObjectList(data); FENominalGroup.DeleteNominalGroup(list[index].ID); list.RemoveAt(index); data = Serialiser<BONominalGroup>.SerialiseObjectList(list); ViewState["nominalGroups"] = data.ToString(); dlNominalGroup.DataSource = list; dlNominalGroup.DataBind(); } void updateNominalGroup(DataListItem theItem) { XElement data = XElement.Parse(Convert.ToString( ViewState["nominalGroups"])); IList<BONominalGroup> list = Serialiser<BONominalGroup>.DeserialiseObjectList(data); BONominalGroup old = list[theItem.ItemIndex]; BONominalGroup n = new BONominalGroup(); byte id = Convert.ToByte(((TextBox)theItem.FindControl("lblID")).Text); string group = ((TextBox)theItem.FindControl("txtGroup")).Text; bool isPositive = Convert.ToBoolean(((CheckBox)theItem.FindControl("chkIsPositive")).Text); n.ID = id; n.Group = group; n.IsPositive = isPositive; FENominalGroup.UpdateNominalGroup(old, n); list[theItem.ItemIndex] = n; data = Serialiser<BONominalGroup>.SerialiseObjectList(list); ViewState["nominalGroups"] = data.ToString(); } void dlNominalGroup_ItemCommand(object source, DataListCommandEventArgs e) { DataList l = (DataList)source; switch (e.CommandName) { case "SelectRow": { if (l.EditItemIndex == -1) { l.SelectedIndex = e.Item.ItemIndex; l.EditItemIndex = -1; } break; } case "EditRow": { if (l.SelectedIndex == e.Item.ItemIndex) { l.EditItemIndex = e.Item.ItemIndex; } break; } case "DeleteRow": { deleteNominalGroup(e.Item.ItemIndex); l.EditItemIndex = -1; try { l.SelectedIndex = e.Item.ItemIndex; } catch { l.SelectedIndex = -1; } break; } case "CancelRow": { l.SelectedIndex = l.EditItemIndex; l.EditItemIndex = -1; break; } case "SaveRow": { updateNominalGroup(e.Item); try { l.SelectedIndex = e.Item.ItemIndex; } catch { l.SelectedIndex = -1; } l.EditItemIndex = -1; break; } } } Lots of code there, I'm afraid, but it should build. Thanks if anyone manages to spot my silliness. The BONominalGroup class (please ignore my crazy getHash override, I'm not proud of it). IAudit can just be an empty interface here and all will be fine. It used to inherit from another class, I have cleaned that out - so the serialization logic may be broken here. public class BONominalGroup { public BONominalGroup() #region Fields and properties private Int16 _ID; public Int16 ID { get { return _ID; } set { _ID = value; } } private string _group; public string Group { get { return _group; } set { _group = value; } } private bool _isPositve; public bool IsPositive { get { return _isPositve; } set { _isPositve = value; } } #endregion public override bool Equals(object obj) { bool retVal = false; BONominalGroup ng = obj as BONominalGroup; if (ng!=null) if (ng._group == this._group && ng._ID == this.ID && ng.IsPositive == this.IsPositive) { retVal = true; } return retVal; } public override int GetHashCode() { return ToString().GetHashCode(); } public override string ToString() { return "BONominalGroup{ID:" + this.ID.ToString() + ",Group:" + this.Group.ToString() + ",IsPositive:" + this.IsPositive.ToString() + "," + "}"; } #region IXmlSerializable Members public override void ReadXml(XmlReader reader) { reader.ReadStartElement("BONominalGroup"); this.ID = Convert.ToByte(reader.ReadElementString("id")); this.Group = reader.ReadElementString("group"); this.IsPositive = Convert.ToBoolean(reader.ReadElementString("isPositive")); base.ReadXml(reader); reader.ReadEndElement(); } public override void WriteXml(XmlWriter writer) { writer.WriteElementString("id", this.ID.ToString()); writer.WriteElementString("group", this.Group); writer.WriteElementString("isPositive", this.IsPositive.ToString()); // writer.WriteStartElement("BOBase"); // base.WriteXml(writer); writer.WriteEndElement(); } #endregion }

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  • I cannot grok MVC, what it is, and what it is not?

    - by Hao
    I cannot grok what MVC is, what mindset or programming model should I acquire so MVC stuff can instantly "lightbulb" on my head? If not instantly, what simple programs/projects should I try to do first so I can apply the neat things MVC brings to programming. OOP is intuitive and easier, object is all around us, and the benefits of code reuse using OOP-paradigm instantly click to anyone. You can probably talk to anybody about OOP in a few minutes and lecture some examples and they would get it. While OOP somehow raise the intuitiveness aspect of programming, MVC seems to do the opposite. I'm getting negative thoughts that some future employers(or even clients) would look down upon me for not using MVC technology. Though I probably get the skinnable aspect of MVC, but when I try to apply it to my own project, I don't know where to start. And also some programmers even have diverging views on how to accomplish MVC properly. Take this for instance from Jeff's post about MVC: The view is simply how you lay the data out, how it is displayed. If you want a subset of some data, for example, my opinion is that is a responsibility of the model. So maybe some programmers use MVC, but they somehow inadvertently use the View or the Controller to extract a subset of data. Why we can't have a definitive definition of what and how to accomplish MVC properly? And also, when I search for MVC .NET programs, most of it applies to web programs, not desktop apps, this intrigue me further. My guess is, this is most advantageous to web apps, there's not much problem about intermixed view(html) and controller(program code) in desktop apps.

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  • Shortest Path algorithm of a different kind

    - by Ram Bhat
    Hey guys, Lets say you have a grid like this (made randomly) Now lets say you have a car starting randomly from one of the while boxes, what would be the shortest path to go through each one of the white boxes? you can visit each white box as many times as you want and cant Jump over the black boxes. The black boxes are like walls. In simple words you can move from white box to white box only.. You can move in any direction, even diagonally.

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  • Working with foreigh keys - cannot insert

    - by Industrial
    Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that is enforced with foreign keys relations? Thanks!

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  • Aren't Information Expert / Tell Don't Ask at odds with Single Responsibility Principle?

    - by moffdub
    It is probably just me, which is why I'm asking the question. Information Expert, Tell Don't Ask, and SRP are often mentioned together as best practices. But I think they are at odds. Here is what I'm talking about: Code that favors SRP but violates Tell Don't Ask, Info Expert: Customer bob = ...; // TransferObjectFactory has to use Customer's accessors to do its work, // violates Tell Don't Ask CustomerDTO dto = TransferObjectFactory.createFrom(bob); Code that favors Tell Don't Ask / Info Expert but violates SRP: Customer bob = ...; // Now Customer is doing more than just representing the domain concept of Customer, // violates SRP CustomerDTO dto = bob.toDTO(); If they are indeed at odds, that's a vindication of my OCD. Otherwise, please fill me in on how these practices can co-exist peacefully. Thank you. Edit: someone wants a definition of the terms - Information Expert: objects that have the data needed for the operation should host the operation Tell Don't Ask: don't ask objects for data in order to do work; tell the objects to do the work Single Responsibility Principle: each object should have a narrowly defined responsibility

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  • What open source database platform is most easily transferred from my personal machine into a window

    - by Tom
    I would like eventual interaction with MS Dynamics SL and/or MindTouch Core (running on WMware) for eventual intranet and/or internet display. I guess I am asking for front and back end recommendations for a database I am constructing, but since this is my first major project I would greatly appreciate any help and advice. I would also love an opportunity to learn a new language so the code base could be in any language. I do have a few more related questions for discussion; What is the viability of using Google hosting to provide the service to the public for free? Should I implement plone or another CMS if I have a large amount of output? Is there a structuring questionnaire or standards publication I could reference? Does UML diagramming provide additional options for portability? Thank you.

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  • Need help choosing database server

    - by The Pretender
    Good day everyone. Recently I was given a task to develop an application to automate some aspects of stocks trading. While working on initial architecture, the database dilemma emerged. What I need is a fast database engine which can process huge amounts of data coming in very fast. I'm fairly experienced in general programming, but I never faced a task of developing a high-load database architecture. I developed a simple MSSQL database schema with several many-to-many relationships during one of my projects, but that's it. What I'm looking for is some advice on choosing the most suitable database engine and some pointers to various manuals or books which describe high-load database development. Specifics of the project are as follows: OS: Windows NT family (Server 2008 / 7) Primary platform: .NET with C# Database structure: one table to hold primary items and two or three tables with foreign keys to the first table to hold additional information. Database SELECT requirements: Need super-fast selection by foreign keys and by combination of foreign key and one of the columns (presumably DATETIME) Database INSERT requirements: The faster the better :) If there'll be significant performance gain, some parts can be written in C++ with managed interfaces to the rest of the system. So once again: given all that stuff I just typed, please give me some advice on what the best database for my project is. Links or references to some manuals and books on the subject are also greatly appreciated. EDIT: I'll need to insert 3-5 rows in 2 tables approximately once in 30-50 milliseconds and I'll need to do SELECT with 0-2 WHERE clauses queries with similar rate.

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  • adding one time options to items

    - by rap-uvic
    Hello, I'm building an Event Registration site. For any given event, we'll have a handful of items to choose from. I have a table for these items. For each event we might have special options for users. For example, for one of the events new users get to buy an item which is not available to other users. This may not apply to all the events. For other events we might have some other restriction on items. I will obviously be checking this programmatically on application side. I would like to though, set up a column containing flag in the items table. But I don't find it feasible because this condition may only apply to one particular event. I don't want all the future items to have this column. What is a good approach to take in such a situation? Should I create a special "restrictions" table and just do a join? How would I handle this on the application side?

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  • How to Manage project in this scenario

    - by vijay.shad
    Hi All, I am working on a web application which has got good amount of static or pre-login pages. These pages can have some simple forms as well where we would like to capture the visitor's details. Post login, I have got my main application. I am confused about the development and deployment architecture of my application. Post login part of my application has a release cycle of 1-2 months while pre-login pages are to be updated on a weekly basis. It is difficult to make a release of pre-login pages as the overall war also contains post-login application & which sometimes is not release ready. Currently, I have got both these parts bundled in the single war project. Please help me by letting me know the best practices whereby I can achieve following: Manage the releases of these two parts independently. I am using Maven. So is there a way I can share the resources, such as CSS, images etc between these two parts. Header and footer of my application is going to be same on pre-login & post-login pages. I was thinking of deploying these apps as two war files in my tomcat container. But then how will I manage the common resources like Css, images etc. Rgds Vijay

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  • document.getElementById not working in IE

    - by Alloi
    Hi, I am using the below js code in order to change the class when a link is clicked. document.getElementById("gifts").setAttribute("class", "gkvSprite selected"); This is not working in IE but it does in FF and Chrome Then I changed the code to : document.getElementById("gifts").setAttribute("className", "gkvSprite selected"); Then it worked in IE stopped working in FF and Chrome. Could someone please help me out here? Thanks in Advance Alloi

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  • How implement the Open Session in View pattern in NHibernate?

    - by MCardinale
    I'm using ASP.NET MVC + NHibernate + Fluent NHibernate and having a problem with lazy loading. Through this question (http://stackoverflow.com/questions/2519964/how-to-fix-a-nhibernate-lazy-loading-error-no-session-or-session-was-closed), I've discovered that I have to implement the Open Session in View pattern , but I don't know how. In my repositories classes, I use methods like this public ImageGallery GetById(int id) { using(ISession session = NHibernateSessionFactory.OpenSession()) { return session.Get<ImageGallery>(id); } } public void Add(ImageGallery imageGallery) { using(ISession session = NHibernateSessionFactory.OpenSession()) { using(ITransaction transaction = session.BeginTransaction()) { session.Save(imageGallery); transaction.Commit(); } } } And this is my Session Factory helper class: public class NHibernateSessionFactory { private static ISessionFactory _sessionFactory; private static ISessionFactory SessionFactory { get { if(_sessionFactory == null) { _sessionFactory = Fluently.Configure() .Database(MySQLConfiguration.Standard.ConnectionString(MyConnString)) .Mappings(m => m.FluentMappings.AddFromAssemblyOf<ImageGalleryMap>()) .ExposeConfiguration(c => c.Properties.Add("hbm2ddl.keywords", "none")) .BuildSessionFactory(); } return _sessionFactory; } } public static ISession OpenSession() { return SessionFactory.OpenSession(); } } Someone could help me to implements Open Session in View pattern? Thank you.

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  • How to make this OO?

    - by John
    Hello, Sorry for the poor title,I'm new to OOP so I don't know what is the term for what I need to do. I have, say, 10 different Objects that inherit one Object.They have different amount and type of class members,but all of them have one property in common - Visible. type TObj1=class(TObject) private a:integer; ...(More members) Visible:Boolean; end; TObj2=class(TObject) private b:String; ...(More members) Visible:Boolean; end; ...(Other 8 objects) For each of them I have a variable. var Obj1:TObj1; Obj2:TObj2; Obj3:TObj3; ....(Other 7 objects) Rule 1: Only one object can be initialized at a time(others have to be freed) to be visible. For this rule I have a global variable var CurrentVisibleObj:TObject; //Because they all inherit TObject Finally there is a procedure that changes visibility. procedure ChangeObjVisibility(newObj:TObject); begin CurrentVisibleObj.Free; //Free the old object CurrentVisibleObj:=newObj; //assign the new object CurrentVisibleObj:= ??? //Create new object CurrentVisibleObj.Visible:=true; //Set visibility to new object end; There is my problem,I don't know how to initialize it,because the derived class is unknown. How do I do this? I simplified the explanation,in the project there are TFrames each having different controls and I have to set visible/not visible the same way(By leaving only one frame initialized). Sorry again for the title,I'm very new to OOP.

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  • Testing system where App-level and Request-level IoC containers exist

    - by Bobby
    My team is in the process of developing a system where we're using Unity as our IoC container; and to provide NHibernate ISessions (Units of work) over each HTTP Request, we're using Unity's ChildContainer feature to create a child container for each request, and sticking the ISession in there. We arrived at this approach after trying others (including defining per-request lifetimes in the container, but there are issues there) and are now trying to decide on a unit testing strategy. Right now, the application-level container itself is living in the HttpApplication, and the Request container lives in the HttpContext.Current. Obviously, neither exist during testing. The pain increases when we decided to use Service Location from our Domain layer, to "lazily" resolve dependencies from the container. So now we have more components wanting to talk to the container. We are also using MSTest, which presents some concurrency dilemmas during testing as well. So we're wondering, what do the bright folks out there in the SO community do to tackle this predicament? How does one setup an application that, during "real" runtime, relies on HTTP objects to hold the containers, but during test has the flexibility to build-up and tear-down the containers consistently, and have the ServiceLocation bits get to those precise containers. I hope the question is clear, thanks!

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  • Building a many-to-many db schema using only an unpredictable number of foreign keys

    - by user1449855
    Good afternoon (at least around here), I have a many-to-many relationship schema that I'm having trouble building. The main problem is that I'm only working with primary and foreign keys (no varchars or enums to simplify things) and the number of many-to-many relationships is not predictable and can increase at any time. I looked around at various questions and couldn't find something that directly addressed this issue. I split the problem in half, so I now have two one-to-many schemas. One is solved but the other is giving me fits. Let's assume table FOO is a standard, boring table that has a simple primary key. It's the one in the one-to-many relationship. Table BAR can relate to multiple keys of FOO. The number of related keys is not known beforehand. An example: From a query FOO returns ids 3, 4, 5. BAR needs a unique key that relates to 3, 4, 5 (though there could be any number of ids returned) The usual join table does not work: Table FOO_BAR primary_key | foo_id | bar_id | Since FOO returns 3 unique keys and here bar_id has a one-to-one relationship with foo_id. Having two join tables does not seem to work either, as it still can't map foo_ids 3, 4, 5 to a single bar_id. Table FOO_TO_BAR primary_key | foo_id | bar_to_foo_id | Table BAR_TO_FOO primary_key | foo_to_bar_id | bar_id | What am I doing wrong? Am I making things more complicated than they are? How should I approach the problem? Thanks a lot for the help.

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  • Program to find canonical cover or minimum number of functional dependencies

    - by Sev
    I would like to know if there is a program or algorithm to find canonical cover or minimum number of functional dependencies? For example: If you have: R = (A,B,C) <-- these are tables: A,B,C And dependencies: A ? BC B ? C A ? B AB ? C The canonical cover (or minimum number of dependencies) is: A ? B B ? C Is there a program that can accomplish this? If not, any code/pseudocode to help me write one would be appreciated. Prefer in Python or Java.

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  • Evenly select N elems from array

    - by ninuhadida
    Hi, I need to evenly select n elements from an array. I guess the best way to explain is by example. say I have: array [0,1,2,3,4] and I need to select 3 numbers.. 0,3,4. of course, if the array length <= n, I just need to return the whole array. I'm pretty sure there's a defined algorithm for this, been trying to search, and I took a look at Introduction to algorithms but couldn't find anything that met my needs (probably overlooked it) The problem I'm having is that I can't figure out a way to scale this up to any array [ p..q ], selecting N evenly elements. note: I can't just select the even elements from the example above.. A couple other examples; array[0,1,2,3,4,5,6], 3 elements ; I need to get 0,3,6 array[0,1,2,3,4,5], 3 elements ; I need to get 0, either 2 or 3, and 5

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  • How to properly name record creation(insertion) datetime field ?

    - by alpav
    If I create a table with datetime default getdate() field that is intended to keep date&time of record insertion, which name is better to use for that field ? I like to use Created and I've seen people use DateCreated or CreateDate. Other possible candidates that I can think of are: CreatedDate, CreateTime, TimeCreated, CreateDateTime, DateTimeCreated, RecordCreated, Inserted, InsertedDate, ... From my point of view anything with Date inside name looks bad because it can be confused with date part in case if I have 2 fields: CreateDate,CreateTime, so I wonder if there are any specific recommendations/standards in that area based on real reasons, not just style, mood or consistency. Of course, if there are 100 existing tables and this is table 101 then I would use same naming convention as used in those 100 tables for the sake of consistency, but this question is about first table in first database in first server in first application.

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  • Algorithm for max integer in an array of integers

    - by gagneet
    Explain which algorithm you would use to implement a function that takes an array of integers and returns the maximum integer in the collection, assuming that the length of the array is less than 1000. Would you use Bubble Sort or Merge Sort and Why? Also, what happens to the above algorithm choice, if the array length is greater than 1000?

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  • Should this even be a has_many :through association?

    - by GoodGets
    A Post belongs_to a User, and a User has_many Posts. A Post also belongs_to a Topic, and a Topic has_many Posts. class User < ActiveRecord::Base has_many :posts end class Topic < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base belongs_to :user belongs_to :topic end Well, that's pretty simple and very easy to set up, but when I display a Topic, I not only want all of the Posts for that Topic, but also the user_name and the user_photo of the User that made that Post. However, those attributes are stored in the User model and not tied to the Topic. So how would I go about setting that up? Maybe it can already be called since the Post model has two foreign keys, one for the User and one for the Topic? Or, maybe this is some sort of "one-way" has_many through assiociation. Like the Post would be the join model, and a Topic would has_many :users, :through = :posts. But the reverse of this is not true. Like a User does NOT has_many :topics. So would this even need to be has_many :though association? I guess I'm just a little confused on what the controller would look like to call both the Post and the User of that Post for a give Topic. Edit: Seriously, thank you to all that weighed in. I chose tal's answer because I used his code for my controller; however, I could have just as easily chosen either j.'s or tim's instead. Thank you both as well. This was so damn simple to implement, and I think today marks the day that I'm beginning to fall in love with rails.

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