Delegate getting nil while using protocol

Question

I want to call a method FromFilter: located in ProductListViewController from other class FilterViewController ,

when i try to call a method i am getting nil value of delegate,

Here is my code snippet:

ProductListViewController.h

@protocol FirstControllerDelegate<NSObject>
@required
-(void)FromFilter:(NSString *)StrApi;

@end

@interface ProductListViewController : UIViewController<FirstControllerDelegate>{
   ....
}
@property (nonatomic, assign) id <FirstControllerDelegate> delegate;

ProductListViewController.m

-(void)FromFilter:(NSString *)StrApi{
    NSLog(@"------- this is not getting called ---------");
}

FilterViewController.h

@interface FilterViewController : UIViewController{
    ...
}
@property (nonatomic, assign) id <FirstControllerDelegate> delegate;

FilterViewController.m

    - (IBAction)ApplyClicked:(id)sender {

    // -----  Here my _delegate is nil ------

    if (_delegate == nil) {
        [_delegate FromFilter:@"fuyds"];
    }

    [self dismissViewControllerAnimated:YES completion:nil];
}

Please help, where i am doing mistake?

Answer 1

It seems to be you didn't assign the delegate property of "FilterViewController".

whenever you create FilterViewController

Example :

FilterViewController *filterViewController = [[FilterViewController alloc]init];

filterViewController.delegate  = self;//important

If you are presenting FilterViewController from ProductListViewController then you should assign the delegate as self

Answer 2

if (_delegate == nil) {
        [_delegate FromFilter:@"fuyds"];
    }

Of course your FromFilter method isn't called. Your code calls this method of _delegate object only if _delegate is nil. Essentially, your code is this:

[nil FromFilter];

In Objective C you can send messages to nil , they simply do nothing and return 0 (nil, NULL).

Answer 3

Did you try to change the code to:

- (IBAction)ApplyClicked:(id)sender {

// -----  Here my _delegate is nil ------

if (_delegate != nil) { // != NOT == --> you want to enter the if clause if the delegate is NOT nil
    [_delegate FromFilter:@"fuyds"];
}

    [self dismissViewControllerAnimated:YES completion:nil];
}