init instance variable multiple times

Question

can this code cause any potential trouble?

@property (nonatomic, retain) NSDictionary *instanceDictionary;

for(int i = 0; i < 50; i++){
   self.instanceDictionary = [NSDictionary alloc] init];
}

or without self

for(int i = 0; i < 50; i++){
   instanceDictionary = [NSDictionary alloc] init];
}

I came across situations where a instance variable gets "overridden" like this and was wondering if it could cause any memory problems.

you re assigning a new reference to the same variable each time, and that reference gets overwritten. — Marcin D
– Marcin D, Commented Aug 4, 2015 at 14:34

Quentin Hayot · Accepted Answer · 2015-08-04 15:13:32Z

3

It won't cause any "memory problem". In your code, at each loop iteration, the instanceDictionary is replaced with a new one.
ARC will take care of releasing the previous one automatically.
This code is pretty useless though.

answered Aug 4, 2015 at 15:13

Quentin Hayot

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3 Comments

rmaddy Over a year ago

It should be noted that in the first example, the memory wouldn't be a problem under MRC but the 2nd approach would be a huge leak under MRC. Both are fine (but pointless) under ARC.

最白目 Over a year ago

I don´t understand why would the second example be a huge leak under MRC?

Quentin Hayot Over a year ago

Because you assign memory and immediately forget the pointer to it, so you won't be able to release it manually.

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