如何比较两个可选的NSArrays在Swift [英] how to compare two optional NSArrays in Swift

问题描述

我们有两个可选的NSArrays。目标是检查，如果他们是平等的。我的解是

  func isArrayEqualToArray（array1：NSArray ?, array2：NSArray？） - > Bool {
 
 let areBothEmpty：Bool = array1 == nil&& array2 == nil 
 
 var areBothEqual：Bool 
 if！areBothEmpty&& array2！= nil {
 areBothEqual = array1？.isEqualToArray（array2！）？ false 
} else {
 areBothEqual = false 
} 
 
 let result = areBothEqual || areBothEmpty 
 return result 
} 
  

我觉得这有点太冗长。它应该以更简洁和可读的方式做。

解决方案

这很简单：

  func isArrayEqualToArray（array1：NSArray ?, array2：NSArray？） - > Bool {
 return array1 == array2 
} 
  

这里 == 是比较可选项的运算符

  func ==< T：Equatable>（lhs：T？，rhs：T？） - Bool 
  

，如果两个操作数都为 true 是 nil ，或两个
操作数都是非nil，且展开的操作数相等。

另外 NSArray 继承自 NSObject ，符合 Equatable ，
并将与 == 比较使用 isEqual：方法，它是
实现为 isEqualToArray：在 NSArray 。
因此

  array1 == array2 
  

给出与

相同的结果

  array1.isEqualToArray（array2）
  

Let's have two optional NSArrays. The goal is to check, if they are equal. My solution is

func isArrayEqualToArray(array1:NSArray?, array2:NSArray?) -> Bool {

    let areBothEmpty:Bool = array1 == nil && array2 == nil

    var areBothEqual:Bool
    if !areBothEmpty && array2 != nil {
        areBothEqual = array1?.isEqualToArray(array2!) ?? false
    } else {
        areBothEqual = false
    }

    let result = areBothEqual || areBothEmpty
    return result
}

I feel that it is a little too verbose. It should be doable in a more concise and readable way. Does anyone have a better solution?

解决方案

It is quite simple:

func isArrayEqualToArray(array1: NSArray?, array2: NSArray?) -> Bool {
    return array1 == array2
}

does exactly what you want.

Why does it work? Here == is the operator that compares optionals

func ==<T : Equatable>(lhs: T?, rhs: T?) -> Bool

and that gives true if both operands are nil, or of both operands are non-nil and the unwrapped operands are equal.

Also NSArray inherits from NSObject which conforms to Equatable, and comparing NSObjects with == uses the isEqual: method, which is implemented as isEqualToArray: on NSArray. Therefore

array1 == array2

gives the same result as

array1.isEqualToArray(array2)

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