Why block can't capture self? - ios

Question

I used a data object to store an array data and when the data load completes, I have a block callback. But the problem is that there are different instances in the two methods:
#implementation DWHomeData
- (instancetype)initWithDataLoadCompletion:(void (^)(BOOL))completion
DWHomeData *data = [DWHomeData new];
data.dwStatus = [#[] mutableCopy];
_completion = [completion copy];
[self loadStatusData];
return data;//<DWHomeData: 0x7fb481546860>
}
- (void)loadStatusData {
DWHomeParam *param = [DWHomeParam new];
[DWHomeTool fetchHomeStatusWithParam:param success:^(NSArray *statusArr) {
self.dwStatus = statusArr;//self address:<DWHomeData: 0x7fb481548b00>
_completion(YES);
} failure:^(NSError *error) {
}];
}
#end
My callback is:
- (void)viewDidLoad {
[super viewDidLoad];
_homeData = [[DWHomeData alloc] initWithDataLoadCompletion:^(BOOL success) {
[self.tableView reloadData];
}];//_homeData address:<DWHomeData: 0x7fb481546860>
}

Answer 1

It's because you are allocing it twice. The method new is just a wrapper for an alloc and an init.
So when you call [[DWHomeData alloc] initWith... you allocated memory for the first instance of DWHomeData.
Then, inside the initWith... method you are calling new which allocated memory for the second instance of DWHomeData and you return that second instance, but you call loadStatusData on the first instance.
The easiest solution would be to replace that new call with the standard:
self = [super init]; // no alloc
if (self) {
// initialize properties and call methods
}
return self;
Or you can do how I like to do all the time:
+ (instancetype)dataWithCompletion:(void (^)(BOOL))completion { // static method
DWHomeData *data = [DWHomeData new]; // alloc needed
if (data) {
[data loadStatusData];
}
return data;
}
and then call it without allocating:
_homeData = [DWHomeData dataWithCompletion:^(BOOL success) {
[self.tableView reloadData];
}];
so the alloc is wrapped inside the static init method and there is no need to call it outside.