Search Results

Search found 45013 results on 1801 pages for 'example'.

Page 361/1801 | < Previous Page | 357 358 359 360 361 362 363 364 365 366 367 368  | Next Page >

  • Cocoa - calling a VIEW method from the CONTROLLER

    - by eemerge
    Hello everyone, Got a little problem i asked about it before but maybe i didnt ask properly. I have a cocoa application, which amongst other things, must do the following task: - load some images from the disk, store them in an array and display them in a custom view. In the Interface Builder i have a CustomView and an OBJECT that points to TexturesController.h The custom view is a custom class, TextureBrowser. Below is the code for the controller and view: TexturesController #import <Cocoa/Cocoa.h> @class TextureBrowser; @interface TexturesController : NSObject { IBOutlet NSTextField *logWindow; IBOutlet TextureBrowser *textureView; NSMutableArray *textureList; } @property textureView; -(IBAction)loadTextures:(id)sender; -(IBAction)showTexturesInfo:(id)sender; @end TextureBrowser @interface TextureBrowser : NSView { NSMutableArray *textures; } @property NSMutableArray *textures; -(void)loadTextureList:(NSMutableArray *)source; @end These are just the headers. Now , what i need to do is: when loadTextures from the TexturesController is called, after i load the images i want to send this data to the view (TextureBrowser), for example, store it in the NSMutableArray *textures. I tried using the -(void)loadTextureList:(NSMutableArray*)source method from the view, but in the TextureController.m i get a warning : No -loadTextureList method found This is how i call the method : [textureView loadTextureList: textureList]; And even if i run it with the warning left there, the array in the view class doesnt get initialised. Maybe im missing something...maybe someone can give a simple example of what i need to do and how to do it (code). Thanks in advance.

    Read the article

  • Handling close-to-impossible collisions on should-be-unique values

    - by balpha
    There are many systems that depend on the uniqueness of some particular value. Anything that uses GUIDs comes to mind (eg. the Windows registry or other databases), but also things that create a hash from an object to identify it and thus need this hash to be unique. A hash table usually doesn't mind if two objects have the same hash because the hashing is just used to break down the objects into categories, so that on lookup, not all objects in the table, but only those objects in the same category (bucket) have to be compared for identity to the searched object. Other implementations however (seem to) depend on the uniqueness. My example (that's what lead me to asking this) is Mercurial's revision IDs. An entry on the Mercurial mailing list correctly states The odds of the changeset hash colliding by accident in your first billion commits is basically zero. But we will notice if it happens. And you'll get to be famous as the guy who broke SHA1 by accident. But even the tiniest probability doesn't mean impossible. Now, I don't want an explanation of why it's totally okay to rely on the uniqueness (this has been discussed here for example). This is very clear to me. Rather, I'd like to know (maybe by means of examples from your own work): Are there any best practices as to covering these improbable cases anyway? Should they be ignored, because it's more likely that particularly strong solar winds lead to faulty hard disk reads? Should they at least be tested for, if only to fail with a "I give up, you have done the impossible" message to the user? Or should even these cases get handled gracefully? For me, especially the following are interesting, although they are somewhat touchy-feely: If you don't handle these cases, what do you do against gut feelings that don't listen to probabilities? If you do handle them, how do you justify this work (to yourself and others), considering there are more probable cases you don't handle, like a supernonva?

    Read the article

  • Is this an acceptable use of "ASCII arithmetic"?

    - by jmgant
    I've got a string value of the form 10123X123456 where 10 is the year, 123 is the day number within the year, and the rest is unique system-generated stuff. Under certain circumstances, I need to add 400 to the day number, so that the number above, for example, would become 10523X123456. My first idea was to substring those three characters, convert them to an integer, add 400 to it, convert them back to a string and then call replace on the original string. That works. But then it occurred to me that the only character I actually need to change is the third one, and that the original value would always be 0-3, so there would never be any "carrying" problems. It further occurred to me that the ASCII code points for the numbers are consecutive, so adding the number 4 to the character "0", for example, would result in "4", and so forth. So that's what I ended up doing. My question is, is there any reason that won't always work? I generally avoid "ASCII arithmetic" on the grounds that it's not cross-platform or internationalization friendly. But it seems reasonable to assume that the code points for numbers will always be sequential, i.e., "4" will always be 1 more than "3". Anybody see any problem with this reasoning? Here's the code. string input = "10123X123456"; input[2] += 4; //Output should be 10523X123456

    Read the article

  • What is the rationale to not allow overloading of C++ conversions operator with non-member function

    - by Vicente Botet Escriba
    C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From > operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration> operator boost::posix_time::ptime( const boost::chrono::time_point<Clock, Duration>& from) { using namespace boost; typedef chrono::time_point<Clock, Duration> time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast<duration_t>( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast<long>(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. For a more complete description of the problem, see here or on my Boost.Conversion library.. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

    Read the article

  • Fun with casting and inheritance

    - by Vaccano
    NOTE: This question is written in a C# like pseudo code, but I am really going to ask which languages have a solution. Please don't get hung up on syntax. Say I have two classes: class AngleLabel: CustomLabel { public bool Bold; // code to allow the label to be on an angle } class Label: CustomLabel { public bool Bold; // Code for a normal label // Maybe has code not in an AngleLabel (align for example). } They both decend from this class: class CustomLabel: Control { protected bool Bold; } The bold field is exposed as public in the descended classes. No interfaces are available on the classes. Now, I have a method that I want to beable to pass in a CustomLabel and set the Bold property. Can this be done without having to 1) find out what the real class of the object is and 2) cast to that object and then 3) make seperate code for each variable of each label type to set bold. Kind of like this: public void SetBold(customLabel: CustomLabel) { AngleLabel angleLabel; NormalLabel normalLabel; if (angleLabel is AngleLabel ) { angleLabel= customLabel as AngleLabel angleLabel.Bold = true; } if (label is Label) { normalLabel = customLabel as Label normalLabel .Bold = true; } } It would be nice to maybe make one cast and and then set bold on one variable. What I was musing about was to make a fourth class that just exposes the bold variable and cast my custom label to that class. Would that work? If so, which languages would it work for? (This example is drawn from an old version of Delphi (Delphi 5)). I don't know if it would work for that language, (I still need to try it out) but I am curious if it would work for C++, C# or Java. If not, any ideas on what would work? (Remember no interfaces are provided and I can not modify the classes.) Any one have a guess?

    Read the article

  • Is it necessary to var scope loop variables in CFScript?

    - by Mel
    When using CFML and CF9 I usually var scope my loop variables; in this case local.i, for example: <cfloop list="#this.list#" index="local.i"> <cfif Len(local.i) GT 10> // do something </cfif> </cfloop> I recently started converting some stuff into CFScript, and (to my disappointment I found out that there is no way to loop over a list in CFScript) I'm wondering if I should still var scope my loop variables, and how: for (i = 1; LTE ListLen(this.list); i = i + 1 ) { if (Len(ListGetAt(this.list, i) GT 10)) { // do something } } Should I be doing local.i = 1 and local.i = local.i + 1 istead of the sample code in my example? Is it necessary? EDIT: I should also ask if the CFScript form of my CFML loop is correct; I ask because I just noticed that my CFML loop uses a , (comma and space) for the delimiter argument, which seems non-existence in the CFScript version of the loop.

    Read the article

  • Why pseudo-elements :before and :after appear in front of my DIV element and not behind?

    - by Dim13i
    I have a DIV element with this given class: .slideshow { background: white; width: 700px; height: 300px; padding:10px; margin: 0 auto; position: relative; box-shadow: 0px 0px 5px grey, 0px 10px 20px rgba(0,0,0,.1) inset; } I define those two pseudo-elements (:before and :after): .slideshow:before, .slideshow:after { content: " "; background: green; width: 50%; height: 50%; position: absolute; z-index: -10; } My problem is that those two pseudo-elements appear in front of my DIV and not behind. Is there any specific reason for this behaviour? Here is an example: EXAMPLE The Javascript part is a bit messy but i'm still working on it. Also I've noticed that if I delete all the JS part I don't have anymore this problem, but I don't think there is anything in the code that should modify the slideshow DIV SOLVED: The problem is in the javascript part where I have: $('.slideshow').css('-webkit-transform', 'rotate(0deg)'); Removing this line solved the problem. I guess that pseudo-elements :before and :after are not compatible with the property transform.

    Read the article

  • Convert long/lat to pixel x/y on a given picure.

    - by Kalinin
    I have a city "map" (for example - Moscow). She in accuracy repeats the contours the given city in google maps (that is it is copied from google maps and it is a little processed, but the sense remained the same). Also I have object co-ordinates in a city (in co-ordinates of google). Problem: how to convert google co-ordinates to the co-ordinates of my picture (that is in pixels on OX and OY on a picture). That is I receive google-co-ordinates and it is necessary for me to draw this point on my picture. The most desired variant of the answer - is based on javascript, but it is possible and on php. I know that on small scales (for example on city scales) it to make simply enough (it is necessary to learn what google-co-ordinates has one of picture corners, then to learn "price" of one pixel in google-co-ordinates on a picture on axes OX and OY separately). But on the big scales (country scale) "price" of one pixel will be not a constant, and will vary strongly enough and the method described above cannot be applied. How to solve a problem on country scales?

    Read the article

  • MS SQL find and replace in TEXT field

    - by incubushead
    I have a database in MS SQL 2005 that was brought up from SQL 2000 and is still using TEXT type fields instead of varchar(max). I need to find and replace a string of characters in the text field but all of the examples of how to do this that I have found don't seem like they would work for me. It seems the UPDATETEXT command requires that the two parameters "insert_offset" and "delete_length" be set explicitly but the string i am searching for could show up in the text at any point or even at several points in the same cell. My understanding of these two parameters is that the string im searching for will always be in the same place, so that insert_offset is the number of spaces into the text that the UPDATETEXT command will start replacing text. Example: Need to find: &lt;u&gt; and Replace it with: <u> Text field example: *Everyone in the room was <b>&lt;u&gt;tired&lt;/u&gt;.</b><br>Then they woke <b>&lt;u&gt;up&lt;/u&gt;. Can anyone help me out with this? THANKS!

    Read the article

  • c++ exercise question

    - by Djecua
    in need of help on a C++ program that will help a deli owner help her customers.Prompt the user for the number of bagels.if then calculate the customers payment two ways. first it finds the price of the smallest multiple of 13 bagels that is closet to the customer's order. it then calculates the price of the customer's order so that the customer's payment is the smallest amount possible with the customer getting the exact number of bagels ordered. if the first method is the smallest amount the program outputs the number of bagels the customer will receive along with the dollar amount owed and the dollar amount saved. otherwise just print the number of bagels received the dollar amount owed $ 3.80 for a dozen bagels (13 bagels) half a dozen(6 bagels) sing bagel cost $.50 owner of the deli is a honest merchant, customers always get the best price on an order, even if they get more bagels than ordered, for example a customer that orders 10 bagels would pay $ 4.60 (2.60 for a half dozen bagels plus $2.00 for 4 single bagels.merchant gives her customer 13 bagels saving the customer $0.80 If someone can example to me how would i design to give customer extra bagels and how to calculate cost.

    Read the article

  • Suggestions for a django db structure

    - by rh0dium
    Hi Say I have the unknown number of questions. For example: Is the sky blue [y/n] What date were your born on [date] What is pi [3.14] What is a large integ [100] Now each of these questions poses a different but very type specific answer (boolean, date, float, int). Natively django can happily deal with these in a model. class SkyModel(models.Model): question = models.CharField("Is the sky blue") answer = models.BooleanField(default=False) class BirthModel(models.Model): question = models.CharField("What date were your born on") answer = models.DateTimeField(default=today) class PiModel(models.Model) question = models.CharField("What is pi") answer = models.FloatField() But this has the obvious problem in that each question has a specific model - so if we need to add a question later I have to change the database. Yuck. So now I want to get fancy - How do a set up a model where by the answer type conversion happens automagically? ANSWER_TYPES = ( ('boolean', 'boolean'), ('date', 'date'), ('float', 'float'), ('int', 'int'), ('char', 'char'), ) class Questions(models.model): question = models.CharField(() answer = models.CharField() answer_type = models.CharField(choices = ANSWER_TYPES) default = models.CharField() So in theory this would do the following: When I build up my views I look at the type of answer and ensure that I only put in that value. But when I want to pull that answer back out it will return the data in the format specified by the answer_type. Example 3.14 comes back out as a float not as a str. How can I perform this sort of automagic transformation? Or can someone suggest a better way to do this? Thanks much!!

    Read the article

  • Is it necessary to mysql real escape when using alter table?

    - by cgwebprojects
    I noticed the other day that I cannot bind variables when using PDO with ALTER TABLE for example the following example will not work, $q = $dbc -> prepare("ALTER TABLE emblems ADD ? TINYINT(1) UNSIGNED NOT NULL DEFAULT '0', ADD ? DATETIME NOT NULL"); $q -> execute(array($emblemDB, $emblemDB . 'Date')); So is it necessary to use mysql_real_escape string and do it like below, // ESCAPE NAME FOR MYSQL INSERTION $emblemDB = mysql_real_escape_string($emblemDB); // INSERT EMBLEM DETAILS INTO DATABASE $q = $dbc -> prepare("ALTER TABLE emblems ADD " . $emblemDB . " TINYINT(1) UNSIGNED NOT NULL DEFAULT '0', ADD " . $emblemDB . "Date DATETIME NOT NULL"); $q -> execute(); Or do I not need to add in mysql_real_escape_string? As the only thing the query can do is ADD columns? Thanks

    Read the article

  • Using list() to extract a data.table inside of a function

    - by Nathan VanHoudnos
    I must admit that the data.table J syntax confuses me. I am attempting to use list() to extract a subset of a data.table as a data.table object as described in Section 1.4 of the data.table FAQ, but I can't get this behavior to work inside of a function. An example: require(data.table) ## Setup some test data set.seed(1) test.data <- data.table( X = rnorm(10), Y = rnorm(10), Z = rnorm(10) ) setkey(test.data, X) ## Notice that I can subset the data table easily with literal names test.data[, list(X,Y)] ## X Y ## 1: -0.8356286 -0.62124058 ## 2: -0.8204684 -0.04493361 ## 3: -0.6264538 1.51178117 ## 4: -0.3053884 0.59390132 ## 5: 0.1836433 0.38984324 ## 6: 0.3295078 1.12493092 ## 7: 0.4874291 -0.01619026 ## 8: 0.5757814 0.82122120 ## 9: 0.7383247 0.94383621 ## 10: 1.5952808 -2.21469989 I can even write a function that will return a column of the data.table as a vector when passed the name of a column as a character vector: get.a.vector <- function( my.dt, my.column ) { ## Step 1: Convert my.column to an expression column.exp <- parse(text=my.column) ## Step 2: Return the vector return( my.dt[, eval(column.exp)] ) } get.a.vector( test.data, 'X') ## [1] -0.8356286 -0.8204684 -0.6264538 -0.3053884 0.1836433 0.3295078 ## [7] 0.4874291 0.5757814 0.7383247 1.5952808 But I cannot pull a similar trick for list(). The inline comments are the output from the interactive browser() session. get.a.dt <- function( my.dt, my.column ) { ## Step 1: Convert my.column to an expression column.exp <- parse(text=my.column) ## Step 2: Enter the browser to play around browser() ## Step 3: Verity that a literal X works: my.dt[, list(X)] ## << not shown >> ## Step 4: Attempt to evaluate the parsed experssion my.dt[, list( eval(column.exp)] ## Error in `rownames<-`(`*tmp*`, value = paste(format(rn, right = TRUE), (from data.table.example.R@1032mCJ#7) : ## length of 'dimnames' [1] not equal to array extent return( my.dt[, list(eval(column.exp))] ) } get.a.dt( test.data, "X" ) What am I missing? Update: Due to some confusion as to why I would want to do this I wanted to clarify. My use case is when I need to access a data.table column when when I generate the name. Something like this: set.seed(2) test.data[, X.1 := rnorm(10)] which.column <- 'X' new.column <- paste(which.column, '.1', sep="") get.a.dt( test.data, new.column ) Hopefully that helps.

    Read the article

  • Keeping Linq to SQL alive when using ViewModels (ASP.NET MVC)

    - by Kohan
    I have recently started using custom ViewModels (For example, CustomerViewModel) public class CustomerViewModel { public IList<Customer> Customers{ get; set; } public int ProductId{ get; set; } public CustomerViewModel(IList<Customer> customers, int productId) { this.Customers= customers; this.ProductId= productId; } public CustomerViewModel() { } } ... and am now passing them to my view instead of the Entities themselves (for example, var Custs = repository.getAllCusts(id) ) as it seems good practice to do so. The problem i have encountered is that when using ViewModels; by the time it has got to the the view i have lost the ability to lazy load on customers. I do not believe this was the case before using them. Is it possible to retain the ability of Lazy Loading while still using ViewModels? Or do i have to eager load using this method? Thanks, Kohan.

    Read the article

  • In Mercurial, can I apply changes from one file to another file in the same branch?

    - by Stephen
    In the good old days of Subversion, I would sometimes derive a new file from an existing one using svn copy. Then if something changed in sections they had in common, I could still use svn merge to update the derived version. To use the example from hginit.com, say the "guac" recipe already exists, and I want to create a "superguac" that includes instructions on how to serve guacamole to 1000 raving soccer fans. Using the process I just described, I could: svn cp guac superguac svn ci -m "Created superguac by copying guac" (edit superguac) svn ci -m "Added instructions for serving 1000 raving soccer fans to superguac" (edit guac) svn ci -m "Fixed a typo in guac" svn merge -r3:4 guac superguac and thus the typo fix would be applied to superguac. Mercurial provides an hg copy command that marks a file as a copy of the original, but I'm not sure the repository structure supports a similar workflow. Here's the same example, and I carefully only edit a single file in the commit I want to use in the merge: hg cp guac superguac hg ci -m "Created superguac by copying guac" (edit superguac) hg ci -m "Added instructions for serving 1000 raving soccer fans to superguac" (edit guac) hg ci -m "Fixed a typo in guac" I now want to apply the change in guac to superguac. Is that possible? If so, what's the right command? Is there a different workflow in Mercurial that achieves the same results (limited to a single branch)?

    Read the article

  • mysql get table based on common column between two tables

    - by Zentdayn
    while trying to learn sql i came across "Learn SQL The Hard Way" and i started reading it. Everything was going fine then i thought ,as a way to practice, to make something like given example in the book (example consists in 3 tables pet,person,person_pet and the person_pet table 'links' pets to their owners). I made this: report table +----+-------------+ | id | content | +----+-------------+ | 1 | bank robbery| | 2 | invalid | | 3 | cat on tree | +----+-------------+ notes table +-----------+--------------------+ | report_id | content | +-----------+--------------------+ | 1 | they had guns | | 3 | cat was saved | +-----------+--------------------+ wanted result +-----------+--------------------+---------------+ | report_id | report_content | report_notes | +-----------+--------------------+---------------+ | 1 | bank robbery | they had guns | | 2 | invalid | null or '' | | 3 | cat on tree | cat was saved | +-----------+--------------------+---------------+ I tried a few combinations but no success. My first thought was SELECT report.id,report.content AS report_content,note.content AS note_content FROM report,note WHERE report.id = note.report_id but this only returns the ones that have a match (would not return the invalid report). after this i tried adding IF conditions but i just made it worse. My question is, is this something i will figure out after getting past basic sql or can this be done in simple way? Anyway i would appreciate any help, i pretty much lost with this. Thank you. EDIT: i have looked into related questions but havent yet found one that solves my problem. I probably need to look into other statements such as join or something to sort this out.

    Read the article

  • Dealing with image upload on server

    - by user1073320
    I have got a the following problem: I have got multi-step form where in one step user upload image to server and then few steps further supplies other information, when this information is invalid no data should be commited - also the image should be deleted. I was thinking about PHP session, but I've read here PHP - Store Images in SESSION data? that it is inefficient way. Every time you proceed step in the form the image is reloaded (in the session) and as somebody mentioned "You will want it to only be as big as it needs to be and you need to delete it as soon as you don't need it because large pieces of information in the session will slow down the session startup." - here i got a question: will it slow down the stratup the session of user who upload file or sessions of all users? I have to mention that I'm looking for solution that doesn't rely on operating system scripts (cron or etc) - I have no permission to run such scripts. The perfect solution for me would be: saving image on disk (for example in some folder named after session id) then after the latest step of form move this image or delete depending on form validation. If user unexpectedly destroy the session (for example closing the browser) of course the folder with image should be deleted. In nutshell I need somethig like callback to event "destroying session".

    Read the article

  • summing functions handles in matlab

    - by user552231
    Hi I am trying to sum two function handles, but it doesn't work. for example: y1=@(x)(x*x); y2=@(x)(x*x+3*x); y3=y1+y2 The error I receive is "??? Undefined function or method 'plus' for input arguments of type 'function_handle'." This is just a small example, in reality I actually need to iteratively sum about 500 functions that are dependent on each other. EDIT The solution by Clement J. indeed works but I couldn't manage to generalize this into a loop and ran into a problem. I have the function s=@(x,y,z)((1-exp(-x*y)-z)*exp(-x*y)); And I have a vector v that contains 536 data points and another vector w that also contains 536 data points. My goal is to sum up s(v(i),y,w(i)) for i=1...536 Thus getting one function in the variable y which is the sum of 536 functions. The syntax I tried in order to do this is: sum=@(y)(s(v(1),y,z2(1))); for i=2:536 sum=@(y)(sum+s(v(i),y,z2(i))) end

    Read the article

  • call back function set by JS settimeout doesn't work in IE8....

    - by NAG
    <html <head <script function addEvent( obj, type, fn ) { if ( obj.attachEvent ) { obj['e'+type+fn] = fn; obj[type+fn] = function(){obj['e'+type+fn]( window.event );} obj.attachEvent( 'on'+type, obj[type+fn] ); } else obj.addEventListener( type, fn, false ); } </script </head <body <!-- HTML for example event goes here -- <div id="mydiv" style="border: 1px solid black; width: 100px; height: 100px; margin-top: 10px;"</div <script // Script for example event goes here addEvent(document.getElementById('mydiv'), 'contextmenu', function(event) { display_short('right-clicked (contextmenu)'); }); function display_short(str) { clearTimeout(); document.getElementById('mydiv').innerHTML = str; if (str != '') alert("hello"); setTimeout("display_short('abcd')", 1000); } </script </body </html Behaves diffrently in IE and FF when you right click on the div area. In ff display_short will be called for evry 1 sec eventhough you dont release right click but in IE it will not call display_short if you dont release right click. But i expect in IE it should call display_short for every 1 sec if you dont release also. Is there any solution for this?

    Read the article

  • iPhone: Helpful Classes or extended Subclasses which should have been in the SDK

    - by disp
    This is more a community sharing post than a real question. In my iPhone OS projects I'm always importing a helper class with helpful methods which I can use for about every project. So I thought it might be a good idea, if everyone shares some of their favorite methods, which should have been in everyones toolcase. I'll start with an extension of the NSString class, so I can make strings with dates on the fly providing format and locale. Maybe someone can find some need in this. @implementation NSString (DateHelper) +(NSString *) stringWithDate:(NSDate*)date withFormat:(NSString *)format withLocaleIdent:(NSString*)localeString{ NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; //For example @"de-DE", or @"en-US" NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:localeString]; [dateFormatter setLocale:locale]; // For example @"HH:mm" [dateFormatter setDateFormat:format]; NSString *string = [dateFormatter stringFromDate:date]; [dateFormatter release]; [locale release]; return string; } @end I'd love to see some of your tools.

    Read the article

  • What is the difference between Inversion of Control and Dependency injection in C++?

    - by rlbond
    I've been reading recently about DI and IoC in C++. I am a little confused (even after reading related questions here on SO) and was hoping for some clarification. It seems to me that being familiar with the STL and Boost leads to use of dependency injection quite a bit. For example, let's say I made a function that found the mean of a range of numbers: template <typename Iter> double mean(Iter first, Iter last) { double sum = 0; size_t number = 0; while (first != last) { sum += *(first++); ++number; } return sum/number; }; Is this dependency injection? Inversion of control? Neither? Let's look at another example. We have a class: class Dice { public: typedef boost::mt19937 Engine; Dice(int num_dice, Engine& rng) : n_(num_dice), eng_(rng) {} int roll() { int sum = 0; for (int i = 0; i < num_dice; ++i) sum += boost::uniform_int<>(1,6)(eng_); return sum; } private: Engine& eng_; int n_; }; This seems like dependency injection. But is it inversion of control? Also, if I'm missing something, can someone help me out?

    Read the article

  • How can I manage a FIFO-queue in an database with SQL?

    - by Jonas
    I have two tables in my database, one for In and one for Out. They have two columns, Quantity and Price. How can I write a SQL-query that selects the correct price? In example: If I have 3 items in for 75 and then 3 items in for 80. Then I have two out for 75, and the third out should be for 75 (X) and the fourth out should be for 80 (Y). How can I write the price query for X and Y? They should use the price from the third and forth row. In example, is there any way to SELECT the third row in the In-table? I can not use auto_increment as identifier for i.e. "third" row, because the tables will contain post for other items too. The rows will not be deleted, they will be saved for accountability reasons. SELECT Price FROM In WHERE ...? NEW database design: +----+ | In | +----+------+-------+ | Supply_ID | Price | +-----------+-------+ | 1 | 75 | | 1 | 75 | | 1 | 75 | | 2 | 80 | | 2 | 80 | +-----------+-------+ +-----+ | Out | +-----+-------+-------+ | Delivery_ID | Price | +-------------+-------+ | 1 | 75 | | 1 | 75 | | 2 | X | <- ? | 3 | Y | <- ? +-------------+-------+ OLD database design: +----+ | In | +----+------+----------+-------+ | Supply_ID | Quantity | Price | +-----------+----------+-------+ | 1 | 3 | 75 | | 2 | 3 | 80 | +-----------+----------+-------+ +-----+ | Out | +-----+-------+----------+-------+ | Delivery_ID | Quantity | Price | +-------------+----------+-------+ | 1 | 2 | 75 | | 2 | 1 | X | <- ? | 3 | 1 | Y | <- ? +-------------+----------+-------+

    Read the article

  • How to catch unintentional function interpositioning?

    - by SiegeX
    Reading through my book Expert C Programming, I came across the chapter on function interpositioning and how it can lead to some serious hard to find bugs if done unintentionally. The example given in the book is the following: my_source.c mktemp() { ... } main() { mktemp(); getwd(); } libc mktemp(){ ... } getwd(){ ...; mktemp(); ... } According to the book, what happens in main() is that mktemp() (a standard C library function) is interposed by the implementation in my_source.c. Although having main() call my implementation of mktemp() is intended behavior, having getwd() (another C library function) also call my implementation of mktemp() is not. Apparently, this example was a real life bug that existed in SunOS 4.0.3's version of lpr. The book goes on to explain the fix was to add the keyword static to the definition of mktemp() in my_source.c; although changing the name altogether should have fixed this problem as well. This chapter leaves me with some unresolved questions that I hope you guys could answer: Does GCC have a way to warn about function interposition? We certainly don't ever intend on this happening and I'd like to know about it if it does. Should our software group adopt the practice of putting the keyword static in front of all functions that we don't want to be exposed? Can interposition happen with functions introduced by static libraries? Thanks for the help. EDIT I should note that my question is not just aimed at interposing over standard C library functions, but also functions contained in other libraries, perhaps 3rd party, perhaps ones created in-house. Essentially, I want to catch any instance of interpositioning regardless of where the interposed function resides.

    Read the article

  • Are there equivalents to Ruby's method_missing in other languages?

    - by Justin Ethier
    In Ruby, objects have a handy method called method_missing which allows one to handle method calls for methods that have not even been (explicitly) defined: Invoked by Ruby when obj is sent a message it cannot handle. symbol is the symbol for the method called, and args are any arguments that were passed to it. By default, the interpreter raises an error when this method is called. However, it is possible to override the method to provide more dynamic behavior. The example below creates a class Roman, which responds to methods with names consisting of roman numerals, returning the corresponding integer values. class Roman def romanToInt(str) # ... end def method_missing(methId) str = methId.id2name romanToInt(str) end end r = Roman.new r.iv #=> 4 r.xxiii #=> 23 r.mm #=> 2000 For example, Ruby on Rails uses this to allow calls to methods such as find_by_my_column_name. My question is, what other languages support an equivalent to method_missing, and how do you implement the equivalent in your code?

    Read the article

  • How to wrap a C function whose parameters are pointer to structs, so that it can be called from Lua?

    - by pierr
    I have the follwing C function. How should I wrap it so it can be called from a Lua script? typedef struct tagT{ int a ; int b ; } type_t; int lib_a_f_4(type_t *t) { return t->a * t->b ; } I know how to wrapr it if the function parameter type were int or char *. Should I use table type for a C structure? EDIT: I am using SWIG for the wraping , according to this doc, It seems that I should automatically have this funtion new_type_t(2,3) , but it is not the case. If you wrap a C structure, it is also mapped to a Lua userdata. By adding a metatable to the userdata, this provides a very natural interface. For example, struct Point{ int x,y; }; is used as follows: p=example.new_Point() p.x=3 p.y=5 print(p.x,p.y) 3 5 Similar access is provided for unions and the data members of C++ classes. C structures are created using a function new_Point(), but for C++ classes are created using just the name Point().

    Read the article

< Previous Page | 357 358 359 360 361 362 363 364 365 366 367 368  | Next Page >