将AnyGenerator与Swift 2.2+结合使用(“& in"循环支持自定义类) [英] Using AnyGenerator with Swift 2.2+ ("for in" loop support for custom classes)
问题描述
以前，我使用以下函数使我的自定义类符合SequenceType协议:
Previously I was using the following function to make my custom class conform to the SequenceType protocol:
func generate() -> AnyGenerator<UInt32> {
var nextIndex = 0
return anyGenerator {
if (nextIndex > self.scalarArray.count-1) {
return nil
}
return self.scalarArray[nextIndex++]
}
}
这是对以下两个问题的公认答案的类似实现:
This is a similar implementation to the accepted answers to these two questions:
但是在Swift 2.2更新之后...
'++'已过时:它将在Swift 3中删除
'++' is deprecated: it will be removed in Swift 3
func generate() -> AnyGenerator<UInt32> {
var nextIndex = 0
return AnyGenerator {
if (nextIndex > self.scalarArray.count-1) {
return nil
}
nextIndex += 1
return self.scalarArray[nextIndex]
}
}
但是这会引发索引超出范围错误，因为我实际上需要使用预先递增的索引，然后在返回后将其递增.
But this throws an Index out of range error because I actually need to use the pre-incremented index and then increment it after the return.
现在如何在Swift中对AnyGenerator起作用?(而且，我应该像链接的其他两个答案那样递减而不是递增吗?)
How does this work for AnyGenerator now in Swift? (Also, should I be decrementing rather than incrementing as the other two answers I linked to do?)
推荐答案
(我假设您的代码引用了 struct ScalarString 来自在Swift中使用Unicode代码点.)
(I assume that your code refers to struct ScalarString
from Working with Unicode code points in Swift.)
确定后，您可以进行Swift 2.2+兼容的增量索引"返回值"和 defer :
You can do a Swift 2.2+ compatible "increment index after determining
the return value" with defer:
func generate() -> AnyGenerator<UInt32> {
var nextIndex = 0
return AnyGenerator {
if nextIndex >= self.scalarArray.count {
return nil
}
defer {
nextIndex += 1
}
return self.scalarArray[nextIndex]
}
}
但是，在您的特殊情况下，转发
In your special case however, it would be easier to just forward the generator of the
private var scalarArray: [UInt32] = []
财产，可以直接:
func generate() -> IndexingGenerator<[UInt32]> {
return scalarArray.generate()
}
或作为转发 next()方法的类型擦除生成器到数组生成器:
or as a type-erased generator which forwards the next() method
to the array generator:
func generate() -> AnyGenerator<UInt32> {
return AnyGenerator(scalarArray.generate())
}
这篇关于将AnyGenerator与Swift 2.2+结合使用(“& in"循环支持自定义类)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
