CODEWITHSUNDEEP
objective-c
propstm
propstm

Reputation: 3629

using [self setVariable:value] vs variable = value

In Objective C what scenario would I want to use [self setVariable:value]; instead of variable = value;

It seems as if doing a self set I'm saving myself few lines of code, but what other advantages are there? Additionally, when would I NOT want to do a self set?

Upvotes: 2

Views: 280

Answers (3)

Dan F
Dan F

Reputation: 17732

EDIT: I should clarify, that what I am referencing below is strictly in regards to variables that are properties. If a variable is just an ivar, then there is no difference between self.variable = value or variable = value, other than the fact that self.variable = value will not even compile if it is just an ivar, in that case you need to use self->variable = value

Calling 

[self setVariable:value];

is the same as calling

self.variable = value;

This, however, is NOT the same as 

variable = value;

The first two cases use the synthesized setVariable method (or the one you defined yourself). The reason you would want to use this is to make sure you keep the proper retain count on your objects.

For example, a simple property such as:

@property (retain) NSString *myString;

Gets an automatically generated set function that looks something like:

-(void) setMyString:(NSString*)other
{
    myString = [other retain];
}

If you were to just call

myString = otherString;

elsewhere in your code, then myString is not retained properly, so if otherString gets deallocated, your pointer to that object is no longer valid.

Upvotes: 3

trojanfoe
trojanfoe

Reputation: 122391

You definitely need to use it when holding objects that require retaining and releasing in order to conform to the Objective-C memory management model. For example:

MyObject.h:

@interface MyObject : NSObject
{
    NSString *_name;
}
@property (retain, nonatomic, readwrite) NSString *name;

@end

MyObject.m:

@implementation MyObject

@synthesize name = _name;

- (id)init
{
    self = [super init];
    if (self != nil)
    {
        self.name = [NSString stringWithFormat:@"name:%d", 12];
    }
    return self;
}

- (void)dealloc
{
    self.name = nil;
    [super dealloc];
}

@end

For data types like int, float, etc., that don't require memory management you can get away without using the setter/getter methods, however it's good practice to use them all the time.

Upvotes: 0

rishi
rishi

Reputation: 11839

The main reason of using setter over assigning value to variable is to achieve Encapsulation.

Some Benefits are -

  1. Encapsulation with getting or setting the property allows additional functionality (like validation) to be added more easily later.
  2. Hiding the instance variable.
  3. Effective memory management.

Upvotes: 1

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