将 NSArray 转换为 Swift Array<T> 并过滤掉不匹配 T 的元素

Question

将 NSArray 转换为 T 类型的 Swift Array 很容易，如果所有元素确实已经是 T 类型的话：

let arr1 : NSArray = [1,2,3]
let arr2 = arr1 as? Array<Int> // works

但现在假设一个非同质 NSArray 对象不匹配 T:

let arr1 : NSArray = [1,2,3,"a"]
let arr2 = arr1 as? Array<Int> // nil, as not all elements are of type Int

我试图实现的是过滤掉所有不匹配的元素的向下转换 T。所以在上面的例子中，我想得到一个 Array<Int> 只包含对象 [1,2,3]。

如何优雅地做到这一点？

Answer 1

压缩：

let arr1 : NSArray = [1,2,3,"a"]
let arr2 = (arr1 as Array<AnyObject>).filter { [=10=] is Int } as! Array<Int>

一步一步：

let arr2 = arr1 as Array<AnyObject>  // convert NSArray to Array of AnyObject
let arr3 = arr2.filter { [=11=] is Int } // keep only objects that are of type Int
let arr4 = arr3 as! Array<Int>       // force cast to Array<Int>, as now you know that all objects are of that type

将 NSArray 转换为 Swift Array<T> 并过滤掉不匹配 T 的元素

Convert NSArray to Swift Array<T> and filter out Elements not matching T

casting

objective-c

nsarray

ios