Extract block parameter

- (void)performLogin {
    // ...
    [self.loginModel loginWithEmail:email password:password completion:^(BOOL success) {
        // This code block will be extracted
        if (success) {
            [self showAlertLoginSuccess];
        } else {
            [self showAlertLoginFailed];
        }
    }];
}
- (IBAction)buttonLoginPressed:(id)sender {
    // Method's call
    [self performLogin];
}

- (void)performLogin:(void (^)(BOOL))completion {
     // ...
    [self.loginModel loginWithEmail:email password:password completion:^(BOOL success) {
        // Extracted block
        completion(success);
    }];
}
- (IBAction)buttonLoginPressed:(id)sender {
    // Method's call with the extracted block
    // as a parameter
    [self performLogin:^(BOOL controller) {
        if (controller) {
            [self showAlertLoginSuccess];
        } else {
            [self showAlertLoginFailed];
        }
    }];
}