How to get variable which is return from method - objective-c

Question

I have two methods and I need to use a variable from first as input parameter in the second. How can I do it? My code is :
First method
-(NSString*)getResponseData :(NSString*) apiHttp {
NSString *code = #"&code=";
NSString *finalLink = [[NSString alloc] initWithFormat:#"%#%#",apiHttp,phoneNumber];
NSURLRequest *request = [NSURLRequest requestWithURL:
[NSURL URLWithString:finalLink]];
NSLog(#"%#", finalLink);
__block NSDictionary *json;
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
json = [NSJSONSerialization JSONObjectWithData:data
options:0
error:nil];
NSLog(#"Async JSON: %#", json);
NSError *error;
NSDictionary *jsonDict = [NSJSONSerialization JSONObjectWithData:data options:0 error:&error];
myString = [jsonDict objectForKey:#"result"];
// NSLog(#"%#", myString);
}];
return myString;
}
Second method:
-(void)showCodeView:(NSString*) ifString{
if([ifString isEqualToString:#"200"]){
aPasswordField.hidden = NO;
[aPasswordField setBorderStyle:UITextBorderStyleLine];
aPasswordField.layer.cornerRadius=1.0f;
aPasswordField.layer.masksToBounds=YES;
aPasswordField.layer.borderColor=[[UIColor whiteColor]CGColor];
aPasswordField.layer.borderWidth= 0.8f;
UIColor *color = [UIColor lightTextColor];
aPasswordField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:#"Код" attributes:#{NSForegroundColorAttributeName: color}];
self.aPasswordField.delegate = self;
}
}
And this is how I call them:
[self getResponseData:apiHttp];
[self showCodeView:myString];
So I can't understand why my myString is null after [self getResponseData:apiHttp]; was called even if my method retutns it.

Answer 1

You are calling two methods after another but are missing that the first one is asynchronous.
When you call sendAsynchronousRequest:queue:completionHandler: it will perform the request asynchronously (not waiting) and call the completion block once it has a response. Since the code doesn't wait for this to happen, getResponseData: immediately returns the current value of myString which is nil if it's not set yet.
You can see how this is working by adding a some log statements before and after each method call:
NSLog(#"Before getResponseData:");
[self getResponseData:apiHttp];
NSLog(#"After getResponseData:");
NSLog(#"Before showCodeView:");
[self showCodeView:myString];
NSLog(#"After showCodeView:");
and the same for the asynchronous request
NSLog(#"Before sendAsynchronousRequest:");
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response,
NSData *data,
NSError *connectionError) {
NSLog(#"After sendAsynchronousRequest:");
// the rest of the completion block ...
There are many ways to deal with this. One would be to add a block argument for the getResponseData: method that is called from the completion handler of the request.
If you are unused to working with blocks, a simpler but more tightly coupled alternative is to call [self showCodeView:myString]; from inside of the completion handler.

Answer 2

You want to perform showCodeView only when your asynchronous getResponseData finishes, so implement your own rendition of the completion block pattern:
- (void)getResponseData :(NSString*) apiHttp completionHandler:(void (^)(NSDictionary *, NSError *))completion {
NSString *code = #"&code=";
NSString *finalLink = [[NSString alloc] initWithFormat:#"%#%#",apiHttp,phoneNumber];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:finalLink]];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
if (completion) {
if (connectionError) {
completion(nil, connectionError);
} else {
NSError *parseError;
NSDictionary *json = [NSJSONSerialization JSONObjectWithData:data options:0 error:&parseError];
completion(json, parseError);
}
}
}];
}
Note, I've eliminated that __block variable and changed the return type to void (since this doesn't return anything ... the value is passed back via the completion block).
You can then do:
[self getResponseData:apiHttp completionHandler:^(NSDictionary *json, NSError *error) {
if (error) {
// handle this however appropriate for your app
} else {
NSString *myString = json[#"result"];
[self showCodeView:myString];
}
}];