NSMutableArray new with Protocol type

Question

How do I get rid of the warning and not use [@[] mutableCopy]:

//Incompatible pointer types assigning to 'NSMutableArray *' from 'NSMutableArray *'

@protocol Coordinatorable <NSObject>

@property (nonatomic, strong, readonly) UINavigationController *presenter;
@property (nonatomic, strong, readonly) NSMutableArray<Coordinatorable>*childCoordinators;

@end


self.childCoordinators = [[NSMutableArray alloc] init]; //Incompatible pointer types assigning to 'NSMutableArray<Coordinatorable> *' from 'NSMutableArray *'
self.childCoordinators = [@[] mutableCopy]; //works without issue

rmaddy · Accepted Answer · 2019-10-04 18:14:24Z

2

I believe the cause of your issue is in how you declare your property. The line:

@property (nonatomic, strong, readonly) NSMutableArray<Coordinatorable>*childCoordinators;

should be:

@property (nonatomic, strong, readonly) NSMutableArray<id<Coordinatorable>>*childCoordinators;

The use of id<SomeeProtocol> is what is needed when referencing objects that conform to the protocol.

answered Oct 4, 2019 at 18:14

rmaddy

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Caleb · Accepted Answer · 2019-10-04 17:35:36Z

1

How do I get rid of the warning and not use [@[] mutableCopy]:

Cast the result:

self.childCoordinators = (NSMutableArray<Coordinatorable>*)[[NSMutableArray alloc] init];

answered Oct 4, 2019 at 17:35

Caleb

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