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  • Configuration and Model-View

    - by HH
    I am using the Model-View pattern on a small application I'm writing. Here's the scenario: The model maintains a list of directories from where it can extract the data that it needs. The View has a Configuration or a Setting dialog where the user can modify this list of directories (the dialog has a JList displaying the list in addition to add and remove buttons). I need some advice from the community: The View needs to communicate these changes to the model. I thought first of adding to the model these methods: addDirectory() and removeDirectory(). But I am trying to limit the number of methods (or channels) that the View can use to communicate with and manipulate the model. Is there any good practice for this? Thank you.

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  • MCV/MVP Patterns and Applications that interface with Hardware (DAQ/PLC/etc)

    - by Ryan
    I've been reading a lot about the MCV and MVP patterns for use with UI and it seems like a really nice powerful way to handle user interfaces. I am - however - having a difficult time deciding how this could integrate into a system where data in the model is created from a Data Acquisition System or Serial/Ethernet devices. There is also the added step that 70% of application interaction is performed by a PLC instead of a live user. It seems that for apps that just read/write & manipulate information from a database this works great, but how does does hardware and automation fit into these patterns? Is it as simple as another controller (for lack of a better term) that interacts with hardware that manipulates data and writes to a model? Maybe I am over thinking this or thinking too simply, so any advice would be great. I'm not quite sure where I'm going with this, so if something doesn't make sense or I was too vague leave me a comment. Thanks!

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  • Why does C# allow abstract class with no abstract members?

    - by fatcat1111
    The C# spec, section 10.1.1.1, states: An abstract class is permitted (but not required) to contain abstract members. This allows me to create classes like this: public abstract class A { public void Main() { // it's full of logic! } } This is really a concrete class; it's only abstract in so far as one can't instantiate it. If inheritors don't actually have to provide implementation, then why call it abstract?

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  • Patterns: Local Singleton vs. Global Singleton?

    - by Mike Rosenblum
    There is a pattern that I use from time to time, but I'm not quite sure what it is called. I was hoping that the SO community could help me out. The pattern is pretty simple, and consists of two parts: A singleton factory, which creates objects based on the arguments passed to the factory method. Objects created by the factory. So far this is just a standard "singleton" pattern or "factory pattern". The issue that I'm asking about, however, is that the singleton factory in this case maintains a set of references to every object that it ever creates, held within a dictionary. These references can sometimes be strong references and sometimes weak references, but it can always reference any object that it has ever created. When receiving a request for a "new" object, the factory first searches the dictionary to see if an object with the required arguments already exits. If it does, it returns that object, if not, it returns a new object and also stores a reference to the new object within the dictionary. This pattern prevents having duplicative objects representing the same underlying "thing". This is useful where the created objects are relatively expensive. It can also be useful where these objects perform event handling or messaging - having one object per item being represented can prevent multiple messages/events for a single underlying source. There are probably other reasons to use this pattern, but this is where I've found this useful. My question is: what to call this? In a sense, each object is a singleton, at least with respect to the data it contains. Each is unique. But there are multiple instances of this class, however, so it's not at all a true singleton. In my own personal terminology, I tend to call the factory method a "global singleton". I then call the created objects "local singletons". I sometimes also say that the created objects have "reference equality", meaning that if two variables reference the same data (the same underlying item) then the reference they each hold must be to the same exact object, hence "reference equality". But these are my own invented terms, and I am not sure that they are good ones. Is there standard terminology for this concept? And if not, could some naming suggestions be made? Thanks in advance...

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  • implementing type inference

    - by deepblue
    well I see some interesting discussions here about static vs. dynamic typing I generally prefer static typing, due to compile type checking, better documented code,etc. However I do agree that they do clutter up the code if done the way Java does it, for example. so Im about to start building a language of my own and type inference is one of the things that I want to implement, in a functional style language... I do understand that it is a big subject, and Im not trying to create something that has not been done before, just basic inferencing... any pointers on what to read up that will help me with this? preferably something more pragmatic/practical as oppose to more theoretical category theory/type theory texts. If there's a implementation discussion text out here, with data structures/algorithms, that would just be lovely much appreciated

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  • Best practice to modularise a large Grails app?

    - by Mulone
    Hi all, A Grails app I'm working on is becoming pretty big, and it would be good to refactor it into several modules, so that we don't have to redeploy the whole thing every time. In your opinion, what is the best practice to split a Grails app in several modules? In particular I'd like to create a package of domain classes + relevant services and use it in the app as a module. Is this possible? Is it possible to do it with plugins? Cheers, Mulone

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  • Should Factories Persist Entities?

    - by mxmissile
    Should factories persist entities they build? Or is that the job of the caller? Pseudo Example Incoming: public class OrderFactory { public Order Build() { var order = new Order(); .... return order; } } public class OrderController : Controller { public OrderController(IRepository repository) { this.repository = repository; } public ActionResult MyAction() { var order = factory.Build(); repository.Insert(order); ... } } or public class OrderFactory { public OrderFactory(IRepository repository) { this.repository = repository; } public Order Build() { var order = new Order(); ... repository.Insert(order); return order; } } public class OrderController : Controller { public ActionResult MyAction() { var order = factory.Build(); ... } } Is there a recommended practice here?

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  • What's a good icon to represent a legend or a key for a diagram?

    - by Bears will eat you
    I'm implementing a small web app widget that shows a legend/key for a diagram (or chart/map/graph/whatever), but only during mouseover of the widget. It's basically just going to be a div with a background image. What would be a good icon that communicates "I show the legend" or "I am the legend" to the unfamiliar users? I'm looking for something in the 10x10 to 20x20 pixel range. Assuming that a legend is the same thing as a key (is it?) then I could use a small icon of a key (like you'd unlock a door with) but that seems cheesy or unclear at worst. I'm not sure that's really the clearest way to do it. Is there an icon that should instantly remind users of a legend?

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  • Auto-generated values for columns in database

    - by Jamal
    Is it a good practice to initialize columns that we can know their values in database, for example identity columns of type unique identifier can have a default value (NEWID()), or columns that shows the record create date can have a default value (GETDATE()). Should I go through all my tables and do this whereever I am sure that I won't need to assign the value manually and the Auto-generated value is correct. I am also thinking about using linq-to-sql classes and setting the "Auto Generated Value" property of these columns to true. Maybe this is what everybody already knows or maybe I am asking a question about a fundamental issue, if so please tell me.

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  • How to export data which are mapped to enumerations

    - by Joshua
    I have a set of data which needs to be imported from a excel sheet, lets take the simplest example. Note: the data might eventually support uploading any locale. e.g. assuming one of the fields denoting a user is gender mapped to an enumeration and stored in the database as 0 for male and 1 for female. 0 and 1 being short values. If I have to import the values I cannot expect the user to punch in numbers (since they are not intuitive and is cumbersome when the enumerations are bigger), what would be the correct way to map to enumerations. Should we ask them to provide a string value in these cases (e.g. male or female) and provide the transformation to a enum in our code by wring a method public static Gender Gender.fromString(String value)

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  • Strange CSS Positioning issue with a fader on a responsive site

    - by EPICWebDesign
    I'm developing a prototype responsive wordpress theme version of my homepage. I'm running into issues with the fader on the homepage. http://dev.epicwebdesign.ca/epicblog/ When the image switches, it uses position:absolute to overlay the pictures, then goes back to position:relative. I need to make the absolute be relative to the bottom left corner of the menu instead of the top left corner of #wrap so it doesn't overlap. I tried putting it in a container div like this: http://wiki.orbeon.com/forms/doc/contributor-guide/browser#TOC-Absolutely-positioned-box-inside-a-box-with-overflow:-auto-or-hidden but that doesn't seem to work. Any ideas? There are major CSS compatibility issues in IE, try it in chrome. It should look similar to http://epicwebdesign.ca. When the browser window is shrunk horizontially, the whole theme compensates.

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  • How to make a jQuery plugin (the right way)?

    - by macek
    I know there are jQuery cookie plugins out there, but I wanted to write one for the sake of better learning the jQuery plugin pattern. I like the separation of "work" in small, manageable functions, but I feel like I'm passing name, value, and options arguments around too much. Is there a way this can be refactored? I'm looking for snippets of code to help illustrate examples provided with in answers. Any help is appreciated. Thanks :) example usage $.cookie('foo', 'bar', {expires:7}); $.cookie('foo'); //=> bar $.cookie('foo', null); $.cookie('foo'); //=> undefined Edit: I did a little bit of work on this. You can view the revision history to see where this has come from. It still feels like more refactoring can be done to optimize the flow a bit. Any ideas? the plugin (function($){ $.cookie = function(name, value, options) { if (typeof value == 'undefined') { return get(name); } else { options = $.extend({}, $.cookie.defaults, options || {}); return (value != null) ? set(name, value, options) : unset(name, options); } }; $.cookie.defaults = { expires: null, path: '/', domain: null, secure: false }; var set = function(name, value, options){ console.log(options); return document.cookie = options_string(name, value, options); }; var get = function(name){ var cookies = {}; $.map(document.cookie.split(';'), function(pair){ var c = $.trim(pair).split('='); cookies[c[0]] = c[1]; }); return decodeURIComponent(cookies[name]); }; var unset = function(name, options){ value = ''; options.expires = -1; set(name, value, options); }; var options_string = function(name, value, options){ var pairs = [param.name(name, value)]; $.each(options, function(k,v){ pairs.push(param[k](v)); }); return $.map(pairs, function(p){ return p === null ? null : p; }).join(';'); }; var param = { name: function(name, value){ return name + "=" + encodeURIComponent(value); }, expires: function(value){ // no expiry if(value === null){ return null; } // number of days else if(typeof value == "number"){ d = new Date(); d.setTime(d.getTime() + (value * 24 * 60 * 60 * 1000)); } // date object else if(typeof value == "object" && value instanceof "Date") { d = value; } return "expires=" + d.toUTCString(); }, path: function(value){ return "path="+value; }, domain: function(value){ return value === null ? null : "domain=" + value; }, secure: function(bool){ return bool ? "secure" : null; } }; })(jQuery);

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  • How to hire a good ui designer

    - by Mark
    I have a webapp that can probably look better. Looking on jobs.stackoverflow, all I see for UI jobs are full-time positions. Is it possible to hire a good UI designer for freelance work? Where would I begin? And anyone know how much I would be looking at?

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  • Doctrine: Relating a model to itself using a link table, like "This event is related to to the following other events"

    - by mattalexx
    So in English, the relationship would sound like "This event is related to to the following other events". My first instinct is to create an EventEvent model, with a first_event_id field and a second_event_id field. Then I would define the following two relationships in the Event model: $this->hasMany('Event as FirstRelatedEvents', array('local' => 'first_event_id', 'foreign' => 'second_event_id', 'refClass' => 'EventEvent')); $this->hasMany('Event as SecondRelatedEvents', array('local' => 'second_event_id', 'foreign' => 'first_event_id', 'refClass' => 'EventEvent')); But I would rather not have to use two relationships on the Event model. Is there a better way to do this?

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  • Which fieldtype is best for storing PRICE values?

    - by BerggreenDK
    Hi there I am wondering whats the best "price field" in MSSQL for a shoplike structure? Looking at this overview: http://www.teratrax.com/sql_guide/data_types/sql_server_data_types.html We have datatypes called money, smallmoney, then we have decimal/numeric and lastly float and real Name, memory/disk-usage and value ranges: Money: 8 bytes (values: -922,337,203,685,477.5808 to +922,337,203,685,477.5807) Smallmoney: 4 bytes (values: -214,748.3648 to +214,748.3647) Decimal: 9 [default, min. 5] bytes (values: -10^38 +1 to 10^38 -1 ) Float: 8 bytes (values: -1.79E+308 to 1.79E+308 ) Real: 4 bytes (values: -3.40E+38 to 3.40E+38 ) My question is: is it really wise to store pricevalues in those types? what about eg. INT? Int: 4 bytes (values: -2,147,483,648 to 2,147,483,647) Lets say a shop uses dollars, they have cents, but I dont see prices being $49.2142342 so the use of a lot of decimals showing cents seems waste of SQL bandwidth. Secondly, most shops wouldn't show any prices near 200.000.000 (not in normal webshops at least... unless someone is trying to sell me a famous tower in Paris) So why not go for an int? An int is fast, its only 4 bytes and you can easily make decimals, by saving values in cents instead of dollars and then divide when you present the values. The other approach would be to use smallmoney which is 4 bytes too, but this will require the math part of the CPU to do the calc, where as Int is integer power... on the downside you will need to divide every single outcome. Are there any "currency" related problems with regionalsettings when using smallmoney/money fields? what will these transfer too in C#/.NET ? Any pros/cons? Go for integer prices or smallmoney or some other? Whats does your experience tell?

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  • How can I refactor this to work without breaking the pattern horribly?

    - by SnOrfus
    I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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  • which is better, creating a materialized view or a new table?

    - by Carson
    I have some demanding mysql queries that are needed to grap same up-to-date datasets from 5-7 mysql tables. I am thinking of creating a table or materialized view to gather all demanding columns from other tables, so as to increase performance. If I create that table, I may need to do extra insert / update / delete operation each time other tables updated. if I create materialized view, I am worrying if the performance can be greatly improved. Because data from other tables are changing very frequently. Most likely, the view may need to be created first everytime before selecting it. Any ideas? e.g. how to cache? other extra measures I can do?

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  • Database Modelling - Conceptually different entities with near identical fields

    - by Andrew Shepherd
    Suppose you have two sets of conceptual entities: MarketPriceDataSet which has multiple ForwardPriceEntries PoolPriceForecastDataSet which has multiple PoolPriceForecastEntry Both different child objects have near identical fields: ForwardPriceEntry has StartDate EndDate SimulationItemId ForwardPrice MarketPriceDataSetId (foreign key to parent table) PoolPriceForecastEntry has StartDate EndDate SimulationItemId ForecastPoolPrice PoolPriceForecastDataSetId (foreign key to parent table) If I modelled them as separate tables, the only difference would be the foreign key, and the name of the price field. There has been a debate as to whether the two near identical tables should be merged into one. Options I've thought of to model this is: Just keep them as two independent, separate tables Have both sets in the one table with an additional "type" field, and a parent_id equalling a foreign key to either parent table. This would sacrifice referential integrity checks. Have both sets in the one table with an additional "type" field, and create a complicated sequence of joining tables to maintain referential integrity. What do you think I should do, and why?

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  • Getting the final value to this MySQL query...

    - by Jack W-H
    I've got my database set up with three tables - code, tags, and code_tags for tagging posts. This will be the SQL query processed when a post is submitted. Each tag is sliced up by PHP and individually inserted using these queries. INSERT IGNORE INTO tags (tag) VALUES ('$tags[1]'); SELECT tags.id FROM tags WHERE tag = '$tags[1]' ORDER BY id DESC LIMIT 1; INSERT INTO code_tags (code_id, tag_id) VALUES ($codeid, WHAT_GOES_HERE?) The WHAT_GOES_HERE? value at the end is what I need to know. It needs to be the ID of the tag that the second query fetched. How can I put that ID into the third query? I hope I explained that correctly. I'll rephrase if necessary.

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  • Best way to determine variable type and treat each one differently in F#

    - by James Black
    I have a function that will create a select where clause, but right now everything has to be a string. I would like to look at the variable passed in and determine what type it is and then treat it properly. For example, numeric values don't have single quotes around them, option type will either be null or have some value and boolean will actually be zero or one. member self.BuildSelectWhereQuery (oldUser:'a) = let properties = List.zip oldUser.ToSqlValuesList sqlColumnList let init = false, new StringBuilder() let anyChange, (formatted:StringBuilder) = properties |> Seq.fold (fun (anyChange, sb) (oldVal, name) -> match(anyChange) with | true -> true, sb.AppendFormat(" AND {0} = '{1}'", name, oldVal) | _ -> true, sb.AppendFormat("{0} = '{1}'", name, oldVal) ) init formatted.ToString() Here is one entity: type CityType() = inherit BaseType() let mutable name = "" let mutable stateId = 0 member this.Name with get() = name and set restnameval=name <- restnameval member this.StateId with get() = stateId and set stateidval=stateId <- stateidval override this.ToSqlValuesList = [this.Name; this.StateId.ToString()] So, if name was some other value besides a string, or stateId can be optional, then I have two changes to make: How do I modify ToSqlValuesList to have the variable so I can tell the variable type? How do I change my select function to handle this? I am thinking that I need a new function does the processing, but what is the best FP way to do this, rather than using something like typeof?

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  • Handling Session ID with Spring

    - by Max
    Hi, I'm trying to build a Spring server for GWT (you can think of it as of Javascript AJAX client). But I can't decide on one point of architecture. How should session be created and used? The obvious easiest way - is to use HTTP sessions (cookies and stuff). Looks fine, but I think that sending session ID separate from the headers would be better (SOAP style). So, what is better: getMyPetsName(String sessionID, int petID) or getMyPetsName(int petID) + session ID through HTTP header (cookies or something). Another question is, if I use the first way (which I like more) - how do I handle session in Spring? I'm really newbie in Spring, and googling did not help. What I mean is: String getMyPetsName(String sessionID, int petID) { Session s = someWayToGetItById(sessionID); } Thanks in advance.

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  • Are today's young programmers getting wrapped around the axle with patterns and practices?

    - by Robert Harvey
    Recently I have noticed a number of questions on SO that look something like this: I am writing a small program to keep a list of the songs that I keep on my ipod. I'm thinking about writing it as a 3-tier MVC Ruby on Rails web application with TDD, DDD and IOC, using a factory pattern to create the classes and a singleton to store my application settings. Do you think I'm taking the right approach? Do you think that we're handing novice programmers a very sharp knife and telling them, "Don't cut yourself with this"? NOTE: Despite the humorous tone, this is a serious (and programming-related) question.

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  • Question about factory classes

    - by devoured elysium
    Currently I have created a ABCFactory class that has a single method creating ABC objects. Now that I think of it, maybe instead of having a factory, I could just make a static method in my ABC Method. What are the pro's and con's on making this change? Will it not lead to the same? I don't foresee having other classes inherit ABC, but one never knows! Thanks

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  • How to use Unique Composite Key

    - by LifeH2O
    I have a table Item(ItemName*, ItemSize*, Price, Notes) I was making composite key of (ItemName,ItemSize) to uniquely identify item. And now after reading some answers on stackoverflow suggesting the use of UNIQUE i revised it as Item(ItemID*, ItemName, ItemSize, Price, Notes) But How to apply UNIQUE constraint on ItemName and ItemSize please correct if there is something wrong in question

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