When would you use self in a method?

Paul Hudson    @twostraws    May 28th 2020

Inside a method, Swift lets us refer to the current instance of a struct using self, but broadly speaking you don’t want to unless you specifically need to distinguish what you mean.

By far the most common reason for using self is inside an initializer, where your likely to want parameter names that match the property names of your type, like this:

struct Student {
    var name: String
    var bestFriend: String

    init(name: String, bestFriend: String) {
        print("Enrolling \(name) in class…")
        self.name = name
        self.bestFriend = bestFriend
    }
}

You don’t have to use that, of course, but it gets a little clumsy adding some sort of prefix to the parameter names:

struct Student {
    var name: String
    var bestFriend: String

    init(name studentName: String, bestFriend studentBestFriend: String) {
        print("Enrolling \(studentName) in class…")
        self.name = studentName
        self.bestFriend = studentBestFriend
    }
}

Outside of initializers, the main reason for using self is because we’re in a closure and Swift requires us to so we’re making it clear we understand what’s happening. From Swift 5.3 or later this situation has greatly improved, meaning that self won’t be needed so much in regular methods.

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