I have a ErrorBlock (errorBlock) defined in my code that can be called multiple times. Though I only want to be informed once about the call, so my idea was to wrap my ErrorBlock (errorBlock) inside another (pErrorBlock) and set that one nil.
Now I wanted to have a cleanup method that sets the references of the innerBlock to nil. But when i hand the inner block over to the cleanup method (Test 1), I have a different result then when I set the inner ErrorBlock nil self (Test 2).
How can I get the result of Test 2, with (a slightly modified) code of Test 1?
My frist Test, shoes a result I don't understand:
-(void)testBlocks{
__block ErrorBlock pErrorBlock= ^(void){
NSLog(@"Foo");
};
NSLog(@"test: %p",pErrorBlock);
ErrorBlock errorBlock = ^(void){
dispatch_async(dispatch_get_main_queue(), ^{
if(pErrorBlock){
NSLog(@"call: %p",pErrorBlock);
pErrorBlock();
}
[self cleanupErrorBlockWith:pErrorBlock];
});
};
errorBlock();
errorBlock();
}
- (void) cleanupErrorBlockWith:(ErrorBlock)errorBlock{
NSLog(@"cleanup: %p",errorBlock);
errorBlock = nil;
NSLog(@"after cleanup: %p",errorBlock);
}
Result:
2013-02-08 16:39:04.484 Tests[9501:907] test: 0x3a6ba8
2013-02-08 16:39:04.496 Tests[9501:907] call: 0x3a6ba8
2013-02-08 16:39:04.497 Tests[9501:907] Foo
2013-02-08 16:39:04.498 Tests[9501:907] cleanup: 0x3a6ba8
2013-02-08 16:39:04.499 Tests[9501:907] after cleanup: 0x0
2013-02-08 16:39:04.500 Tests[9501:907] call: 0x3a6ba8
2013-02-08 16:39:04.501 Tests[9501:907] Foo
2013-02-08 16:39:04.502 Tests[9501:907] cleanup: 0x3a6ba8
2013-02-08 16:39:04.503 Tests[9501:907] after cleanup: 0x0
My second Test, with the desired result is:
-(void)testBlocks{
__block ErrorBlock pErrorBlock= ^(void){
NSLog(@"Foo");
};
NSLog(@"test: %p",pErrorBlock);
ErrorBlock errorBlock = ^(void){
dispatch_async(dispatch_get_main_queue(), ^{
if(pErrorBlock){
NSLog(@"call: %p",pErrorBlock);
pErrorBlock();
NSLog(@"cleanup: %p",pErrorBlock);
pErrorBlock = nil;
NSLog(@"after cleanup: %p",pErrorBlock);
}
});
};
errorBlock();
errorBlock();
}
Result:
2013-02-08 16:42:18.485 Tests[9540:907] test: 0x3a6ba8
2013-02-08 16:42:18.496 Tests[9540:907] call: 0x3a6ba8
2013-02-08 16:42:18.498 Tests[9540:907] Foo
2013-02-08 16:42:18.499 Tests[9540:907] cleanup: 0x3a6ba8
2013-02-08 16:42:18.500 Tests[9540:907] after cleanup: 0x0
You are passing block by value, pass it by reference like this. Also moving you cleanupErrorBlockWith:
call inside if
statement.
-(void)testBlocks{
__block ErrorBlock pErrorBlock= ^(void){
NSLog(@"Foo");
};
NSLog(@"test: %p",pErrorBlock);
ErrorBlock errorBlock = ^(void){
dispatch_async(dispatch_get_main_queue(), ^{
if(pErrorBlock){
NSLog(@"call: %p",pErrorBlock);
pErrorBlock();
[self cleanupErrorBlockWith:&pErrorBlock];
}
});
};
errorBlock();
errorBlock();
}
- (void) cleanupErrorBlockWith:(ErrorBlock*)errorBlock{
NSLog(@"cleanup: %p",*errorBlock);
*errorBlock = nil;
NSLog(@"after cleanup: %p",*errorBlock);
}