CODEWITHSUNDEEP
swiftprotocolsswift-protocols
Bobj-C
Bobj-C

Reputation: 5426

Compare 2 structs/Objects implement the same Protocol?

let's say I have the following :

protocol P : Equatable {
 var uniqueID : Int { get }
}

struct A : P {
 var uniqueID = 1
}

struct B : P {
 var uniqueID = 2
}

func ==<T : P>(lhs:T , rhs:T) -> Bool { return lhs.uniqueID == rhs.uniqueID }

Now when I write the following:

 let a = A()
 let b = B()

 let c = a == b

I got error: binary operator '==' cannot be applied to operands of type 'A' and 'B'

is there any way to achieve this ?

Upvotes: 6

Views: 771

Answers (1)

Daniel Kl&#246;ck
Daniel Kl&#246;ck

Reputation: 21137

you have to define the equality function with two generic types to allow different types to be compared, like this:

func ==<T: P, T2: P>(lhs: T , rhs: T2) -> Bool { return lhs.uniqueID == rhs.uniqueID }

Upvotes: 10

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