Define @property in Protocol

Question

I have a number of UIViewController subclasses and I want them to share the same property called session which handles a "is logged in" state.

I know that I could use a parent class but this is very explicit and so I was wondering if I could "enforce" the session property via a shared protocol.

I have never seen an explicit property defined in a protocol (obviously you could define the setter and getter), so is defining a property inside a protocol an advisable pattern?

Answer 1

@property can also appear in the declaration of a protocol or category.

Stated in the official apple documentation . So no problem there.

Answer 2

您可以在协议中拥有属性，前提是每个符合您协议的类都具有该属性的相应@synthesize ，或者提供getter和setter。

Answer 3

Yes, using a protocol it's possible to add a property:

@protocol MyProtocol <NSObject>

@property (nonatomic, retain) NSFoobar *baz;

@end

And @synthesize baz; in every class that adopts this protocol (or you can mark the declared property as optional using the @optional keyword).

Answer 4

In .h file:

 @property(nonatomic,strong)UILabel *mylabel;

In .m file:

 @synthesize mylabel = _mylabel;

compiler will create getter and setter for mylabel.

Ex -> 

-(void)setMylabe:(UILabel *) mylabel { //setter


}

-(UIlabel*)mylabel { // getter


}