arrays - 如何简化 Swift 数组初始化

Question

这是参考https://stackoverflow.com/a/47765972/8833459。给出以下声明：

let fooPaths: [WritableKeyPathApplicator<Foo>] = [WritableKeyPathApplicator(\Foo.bar), WritableKeyPathApplicator(\Foo.baz)]

是否有一个 init 或其他可以完成的操作，以便以下（或类似的）也可以工作？

let fooPaths: [WritableKeyPathApplicator<Foo>] = [\Foo.bar, \Foo.baz]

原来的说法就是打字太多了！我的“首选”方法目前给出了错误：

error: cannot convert value of type 'WritableKeyPath<Foo, String>' to expected element type 'WritableKeyPathApplicator<Foo>'

Answer 1

类型是不必要的：

let fooPaths = [WritableKeyPathApplicator(\Foo.bar), WritableKeyPathApplicator(\Foo.baz)]

第二个Foo是不必要的。

let fooPaths = [WritableKeyPathApplicator(\Foo.bar), WritableKeyPathApplicator(\.baz)]

如果您确实提供了类型，也是第一个：

let fooPaths: [WritableKeyPathApplicator<Foo>] = [WritableKeyPathApplicator(\.bar),
                                                  WritableKeyPathApplicator(\.baz)]

如果主要关注的是打字，请添加本地类型别名：

typealias WKPA<T> = WritableKeyPathApplicator<T>
let fooPaths: [WKPA<Foo>] = [WKPA(\.bar),
                             WKPA(\.baz)]