【Swift 60秒】64 - Mutating methods

0x00 Lesson

If a struct has a variable property but the instance of the struct was created as a constant. that property can't be changed - the struct is constant, so all its properties are also constant regardless of how they were created.

The problem is that when you create the struct Swift has no idea whether you will use it with constants or variables, so by default it takes the safe approach: Swift won’t let you write methods that change properties unless you specifically request it.

When you want to change a property inside a method, you need to mark it using the mutating keyword, like this:

struct Person {
	var name: String
	mutating func makeAnonymous() {
		name = "Anonymous"
	}
}

Because it changes the property, Swift will only allow that method to be called on Person instances that are variables:

var person = Person(naem: "Ed")
person.makeAnonymous()

---

0x01 我的小作品

欢迎体验我的作品之一：小五笔
五笔学习好帮手
App Store 搜索即可~

---