英文:
Swift: reproducing forEach, viewing source code?
问题
我目前正在学习闭包，我觉得我已经理解了，但我对复制数组的forEach方法很感兴趣。我想看看它是如何实现的。在Xcode中，我可以看到声明，其中显示了：
@inlinable public func forEach(_ body: (Element) throws -> Void) rethrows
但我真正想看到的是实际的代码。
例如，以下代码块：
var items = [1,2,3]
items.forEach { (item) in
print(item)
}
我对闭包如何访问（item）感兴趣，forEach如何提供这些信息。
闭包是我的代码，它接收了我命名为“item”的第一个变量，当然它能正常工作，但我想知道它是如何实现的。
如果我想创建一个新版本的forEach，让我们称它为forEachNew，那么我该如何做呢？
forEach是针对特定类型/协议的扩展吗？
非常感谢任何帮助。
英文:
I am currently learning closures and I think I have it but I am interested in reproducing the forEach method of an array. I would like to see how its done. In xcode I can see the declaration which shows
@inlinable public func forEach(_ body: (Element) throws -> Void) rethrows
but what i really want to see is the actually code.
For example the following
var items = [1,2,3]
items.forEach { (item) in
print(item)
}
I am interested in how the closure has access to (item), how is forEach providing this information.
The closure is my code and it receives the first variable which I have named "item", of course it works but i wanted to know how.
If I wanted to create a new version of forEach, lets call it forEachNew then how would i do this.
Is the forEach an extension over a specific type/ protocol ?
Any help really appreciated.
Thanks
答案1
得分: 3
你可以在GitHub上查看Sequence.forEach的当前实现，因为Swift是开源的。
当前的实现简单地使用for ... in循环来迭代Sequence，然后对每个元素执行body闭包。
@inlinable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
英文:
You can check the current implementation of Sequence.forEach on GitHub, since Swift is open-source.
The current implementation simply uses a for ... in loop to iterate through the Sequence and then executes the body closure for each element.
@inlinable
public func forEach(
_ body: (Element) throws -> Void
) rethrows {
for element in self {
try body(element)
}
}
}
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论