why swift use a struct as dictionary key instead of a string here?

Question

Why UIImagePickerController.InfoKey type is struct not a string ,what is the benefit to use struct as a dictionary key instead of string?

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Answer 1

It's simple, the benefit is the ability to check key values during compilation. This way, you won't be able to pass a String directly and if you do, you have to manually wrap it into a InfoKey structure, making your intention clear.

Most of the times you should be using one of the predefined constants.

An enum would be a better solution but probably that would break some existing code (and cannot be really enforced in Objective-C).

If Apple engineers were creating a new API today, they wouldn't probably even use a dictionary but they would use a custom object to pass the values to the delegate method.