Databases
StackOverflow2013
Postsdbo
POObjective C - Accessors ie Getters/Setters
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POObjective C - Accessors ie Getters/Setters
    primarykey
    data
    text
    <p>I Have read the already posted questions extensively and can't quite find the answer I'm looking for. </p> <p>I fully understand the concept of using the <code>@syntesize</code> directive to create getter and setter methods (i.e. if i had <code>@property int width</code> and <code>@synthesize width</code>, I am inadvertently creating a getter method of <code>width</code> and a setter method of <code>setWidth:</code>). </p> <p>However, when I am not using the <code>@synthesize</code> directive but am declaring instance variables in the <code>@implementation</code> section that are objects, I do not fully understand how the accessor methods work. This is what I do not understand about the following code:</p> <p>1) in <code>main</code> where it says: </p> <pre><code>NSLog(@"Origin at (%i, %i)", myRect.origin1.x, myRect.origin1.y); </code></pre> <p>It appears to me as if it would be calling the <code>[[myRect origin1] x]</code> method which would first determine that <code>[myRect origin1]</code> returns <code>origin</code> and would then immediately call <code>[origin x]</code> as a result (and then do the same for <code>y</code>). Now, what throws me off is the fact that if I were to change the name of the getter method</p> <pre><code>-(XYpoint *) origin1; </code></pre> <p>contained within Rectangle.h to</p> <pre><code>-(XYpoint *) origin2; </code></pre> <p>the program gets tons of errors and ceases to compile. Note: I also changed the name of this method everywhere it is referenced including changing the preceding code in main to</p> <pre><code>NSLog(@"Origin at (%i, %i)", myRect.origin2.x, myRect.origin2.y); </code></pre> <p>However if I also change the name of the setter method from:</p> <pre><code>-(void) setOrigin1: (XYpoint *) pt </code></pre> <p>to:</p> <pre><code>-(void) setOrigin2: (XYpoint *) pt </code></pre> <p>then everything works as it did before. It seems to me it only works correctly when my getter and setter are both named in the <code>x</code> <code>setX</code> naming convention. I supposed this is mainly what I need explained:</p> <p>A) If I create an instance variable that happens to be an object (like 'origin' in this case) must I create getter and setter methods for it?</p> <p>B) Can I create a getter method but not a setter method or vice versa</p> <p>C) Is it mandatory that if I do create both a getter and setter method for 'origin' that they both be named in the <code>x</code> <code>setX</code> manner. In this case as <code>-(XYpoint *) origin1</code> and <code>-(void) setOrigin1: (XYpoint *) pt</code>. As in if I change the name of the getter I must change the name of the setter accordingly?</p> <p>Here is all of the code:</p> <p>Rectangle.h:</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; @class XYpoint; @interface Rectangle : NSObject @property int width, height; -(XYpoint *) origin1; -(void) setOrigin1: (XYpoint *) pt; -(void) setWidth: (int) w andHeight: (int) h; -(int) area; -(int) perimeter; @end </code></pre> <p>Rectangle.m:</p> <pre><code>#import "Rectangle.h" @implementation Rectangle { XYpoint *origin; } @synthesize width, height; -(void) setWidth:(int) w andHeight:(int)h { width = w; height = h; } -(void) setOrigin1: (XYpoint *) pt { origin = pt; } -(int) area { return width * height; } -(int) perimeter { return (width + height) * 2; } -(XYpoint *) origin1 { return origin; } @end </code></pre> <p>XYpoint.h:</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; @interface XYpoint : NSObject @property int x, y; -(void) setX: (int) xVal andY: (int) yVal; @end </code></pre> <p>XYpoint.m:</p> <pre><code>#import "XYpoint.h" @implementation XYpoint @synthesize x,y; -(void) setX: (int) xVal andY: (int) yVal { x = xVal; y = yVal; } @end </code></pre> <p>main.m:</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; #import "Rectangle.h" #import "XYpoint.h" int main (int argc, const char * argv[]) { @autoreleasepool { Rectangle *myRect = [[Rectangle alloc] init]; XYpoint *myPoint = [[XYpoint alloc] init]; [myPoint setX: 100 andY: 200]; [myRect setWidth: 5 andHeight:8]; myRect.origin1 = myPoint; NSLog(@"Rectangle w = %i, h = %i", myRect.width, myRect.height); NSLog(@"Origin at (%i, %i)", myRect.origin1.x, myRect.origin1.y); NSLog(@"Area = %i, Perimeter = %i", [myRect area], [myRect perimeter]); } return 0; } </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USAlex
    1. USReiAndCoke
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POObjective C - Accessors ie Getters/Setters
      1. USennuikiller
      1. VTFavorite
    2. VO
      singulars
      1. POObjective C - Accessors ie Getters/Setters
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POObjective C - Accessors ie Getters/Setters
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThe dot notation is really just shorthand for the accessor calls. Since myRect.origin2 could equate to [myRect origin2] OR [myRect setOrigin2], depending on context, both of those accessors need to be defined in order to use the dot notation. Regardless, you should really be declaring instance variables as properties, as in Jakob's answer.
      singulars
      1. POObjective C - Accessors ie Getters/Setters
      1. USspwert
    2. COThank you! That is exactly my problem. Changing my getter (or setter) from setOrigin1 to setOrigin2 would then mean that when myRect.origin1 is called it essentially needs both a getter/setter named accordingly. And since I changed setOrigin1 to setOrigin2 there is no longer both a getter and setter. Even if I never use it the compiler requires it. At least I believe thats what you mean. If so, it makes sense to me now. Though I don't know how to give you a "correct" answer since its just listed as a comment
      singulars
      1. POObjective C - Accessors ie Getters/Setters
      1. USReiAndCoke
    3. COThis is wrong. You don't need both accessors. If you define `-(int)foo;` in your header file, you can use `int x = myObj.foo;`. On the other hand, if you define `-(void)setBar:(int)anInt;` in the header file, you can use `myObj.bar = 15;`. Getters and setters are independent.
      singulars
      1. POObjective C - Accessors ie Getters/Setters
      1. USJakob Egger
 

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