Swift 4 中键值编码的优势 [英] Advantage of Key-Value Coding in Swift 4

问题描述

我只想知道 Swift 4 中键值编码的好处.因为我很清楚键值编码(保留对属性的引用，而不实际访问该属性所持有的基础数据).

I just want to know the benefits of Key-Value Coding in Swift 4. As I am well aware of key-value coding (hold reference to properties without actually accessing the underlying data held by the property).

例如:

struct Student {
    var name: String?
    var rollNo: String?
}

let student = Student(name: "aman", rollNo: "12121")
let nameKey = \Student.name
let name = student[keyPath: nameKey]

这里我们创建了Student的实例并通过下标(keyPath)访问值，但我可以通过简单地编写代码student.name轻松访问该值.

Here we created the the instance of Student and access the value by subscript (keyPath) but I can easily access the value by simply writing the code student.name.

在 Objective-C 中，我们使用字符串作为键，如下所示，我们可以从中受益

In Objective-C, we use string as a key like given below and we could take some benefits from it

 [object valueForKey:@"name"]

我的问题是编码级别或内存级别有什么好处吗?

My question is that is there any benefits related to coding level or memory level?

推荐答案

两个主要优势是:

1. 已验证密钥:如果您尝试使用无效的密钥，Xcode 会在编译时警告您.

1. Keys are validated: Xcode will warn you, at compile time, if you try to use a key that is not valid.

结果是强类型的: 使用以下内容，编译器将知道结果 name 是一个 String:

Results are strongly typed: With the following, the compiler will know that the resulting name is a String:

let name = student[keyPath: nameKey]

这消除了进行任何转换的需要.

This eliminates the need to do any casting.

结果是编写安全代码要容易得多.

The result is that it's much easier to write safe code.

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