Question

In this 3 cases I will have memory leak?

• No __strong and no set to nil

  - (void)function {
        NSString *string = [[NSString alloc] initWithString: @"Hello World"];
  }
  

• No set to nil but use __strong

  - (void)function {
      __strong NSString *string = [[NSString alloc] initWithString: @"Hello World"];
  }
  

• No __strong but set nil

  - (void)function {
      NSString *string = [[NSString alloc] initWithString: @"Hello World"];
      string = nil;   
  }
  

With Automatic Reference Counting (ARC), if I don’t set any keyword, I assume the variable is __strong?

Answer 1

If you don’t specify an ownership qualifier, it’s implicitly __strong. Then, at the end of the local scope in which the variable is declared, the compiler inserts a release, regardless of whether you set the variable to nil.

So, your local variable is released in all three cases — no leak.