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Nehemiah Reese
17,692 PointsConfused on when to alloc and init an instance in Objective C. Any Advice?
My guess is when you create an instance of a custom class.
2 Answers
Johanns Gregorian
8,694 PointsIt depends on what you are doing, and the specifics of the object class that you are working with -- you'll need to consult implementation/documentation.
Here is a very simple example (and one possibility):
/// Sample.h
@interface Sample : NSObject
@property (strong, nonatomic) NSString *myString;
- (NSString *)instanceMethod;
+ (NSString *)classMethod;
@end
/// Sample.m
@implementation Sample
- (instancetype)init
{
self = [super init];
if (self) {
self.myString = @"I am an instance variable!";
}
return self;
}
- (NSString *)instanceMethod {
return self.myString;
}
+ (NSString *)classMethod {
return @"You called the class method!";
}
@end
In order for you to call instanceMethod, you must allocate (alloc) memory and initialize (init) your object:
Sample *sampleInstance = [[Sample alloc] init];
NSString *someString = [sample instanceMethod];
NSLog(@"%@", someString);
// Prints => "I am an instance variable!"
However, it is not necessary to call alloc or init if you want to use the classMethod:
NSString *anotherString = [Sample classMethod];
NSLog(@"%@", anotherString);
// Prints => "You called the class method!'
I hope this helps, and here are a few links for further reading:
Nehemiah Reese
17,692 PointsYes it helps a lot! Thanks man!