Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Objective-C <strong>only</strong> support passing parameters by value. The problem here has probably been fixed already (Since this question is more than a year old) but I need to clarify some things regarding arguments and Objective-C.</p> <p><a href="http://en.wikipedia.org/wiki/Objective-C#Syntax" rel="noreferrer">Objective-C</a> is a <em>strict superset</em> of C which means that everything C does, Obj-C does it too.</p> <p>By having a quick look at Wikipedia, you can <a href="http://en.wikipedia.org/wiki/C_%28programming_language%29#Characteristics" rel="noreferrer">see</a> that <code>Function parameters are always passed by value</code></p> <p>Objective-C is no different. What's happening here is that whenever we are passing an object to a function (In this case a UILabel *), we pass the value <em>contained</em> at the pointer's address.</p> <p>Whatever you do, it will always be the value of what you are passing. If you want to pass the value of the <em>reference</em> you would have to pass it a **object (Like often seen when passing NSError).</p> <p>This is the same thing with scalars, they are passed by value, hence you can modify the value of the variable you received in your method and that won't change the value of the original variable that you passed to the function.</p> <p>Here's an example to ease the understanding:</p> <pre><code>- (void)parentFunction { int i = 0; [self modifyValueOfPassedArgument:i]; //i == 0 still! } - (void)modifyValueOfPassedArgument:(NSInteger)j { //j == 0! but j is a copied variable. It is _NOT_ i j = 23; //j now == 23, but this hasn't changed the value of i. } </code></pre> <p>If you wanted to be able to modify i, you would have to pass the value of the <em>reference</em> by doing the following:</p> <pre><code>- (void)parentFunction { int i = 0; //Stack allocated. Kept it that way for sake of simplicity [self modifyValueOfPassedReference:&amp;i]; //i == 23! } - (void)modifyValueOfPassedReference:(NSInteger *)j { //j == 0, and this points to i! We can modify i from here. *j = 23; //j now == 23, and i also == 23! } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POPassing arguments by value or by reference in objective C
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USPier-Olivier Thibault
    1. USPier-Olivier Thibault
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POPassing arguments by value or by reference in objective C
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COTechnically, yes, you only pass the primitives by value. However this is entirely misleading in that while the pointer to an object is passed by value, that pointer is pointing to the same object. As there is NO OTHER WAY TO PASS (or deal with) OBJECTS, *objects* are always passed by reference. The only time they behave as if they're not is if OP said labelToChange = nil; or something like that, but that's something everyone here knows wouldn't work and aren't discussing.
      singulars
      1. PO
      1. USJared Pochtar
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload