CODEWITHSUNDEEP
swift
az2902
az2902

Reputation: 428

How to constrain a Dictionary's Value to a protocol

I want a define a typealias for a Dictionary, who's key can only be of type String and value can only be of type that conform to the Encodable protocol. The reason for this is so that I can use JSONEncoder and encode the values later on.

I have tried:

typealias APIParams = [String: T where Value: Encodable] but it throws an error at me.

How can I accomplish this?

Upvotes: 0

Views: 113

Answers (2)

matt
matt

Reputation: 536047

I have tried:

typealias APIParams = [String: T where Value: Encodable]

but it throws an error at me.

Closest to the way you were writing it (with a where clause) would be

typealias APIParams<T> = [String: T] where T: Encodable

Upvotes: 0

Sweeper
Sweeper

Reputation: 275125

If you want to be able to encode a APIParams later on, you should do:

typealias APIParams<T: Encodable> = [String: T]

Type aliases can be generic! You would now be able to say e.g. APIParams<Int>, APIParams<String>, or APIParams<YourCodableStruct>

Upvotes: 1

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