CODEWITHSUNDEEP
objective-cobjectdeclaration
Sahat Yalkabov
Sahat Yalkabov

Reputation: 33624

Object declaration in Objective-C

Is there any difference in declaring objects in Objective-C between (1) and (2), besides the style and personal preference?

(1) One-line declaration, allocation, initialization.

Student *myStudent = [[Student alloc] init];

(2) Multi-line declaration, allocation, initialization.

Student *myStudent;
myStudent = [Student alloc]; 
myStudent = [myStudent init];

Upvotes: 3

Views: 1847

Answers (3)

Kevin Sylvestre
Kevin Sylvestre

Reputation: 38012

Nope, no difference.

Upvotes: 2

Elfred
Elfred

Reputation: 3851

No, there isn't a difference. The [Student alloc] just allocates memory for a pointer, meanwhile [myStudent init] actually sets the initial values.

If you are familiar with C, think of alloc as doing

Student *myStudent = calloc(1, sizeof(Student));

And the init call as a function that sets the initial values.

Upvotes: 4

luvieere
luvieere

Reputation: 37494

In the second case, you can initialize the same object more than once. You send an alloc message to the class to get an uninitialized instance, that you must then initialize, having several ways to do it:

NSString *myStr = [NSString alloc];
NSString *str1 = [myStr init]; //Empty string
NSString *str2 = [myStr initWithFormat:@"%@.%@", parentKeyPath, key];

Upvotes: 2

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