创建一个"forCount" Swift中的控制结构 [英] Create a "forCount" control structure in Swift
问题描述
在许多项目中,此控制结构对于提高可读性非常理想:
In many projects this control structure is ideal for readability:
forCount( 40 )
{
// this block is run 40 times
}
You can do exactly that in objective-C.
鉴于Swift的宏方法与Objective-c的实现非常不同,
Given that Swift has a very different approach to macros than objective-c,
是否可以在Swift项目中创建这样的forCount(40)
控件结构?
is there a way to create such a forCount(40)
control structure in Swift projects?
Swift中的一些相似概念:
Some similar concepts in Swift:
for _ in 1...40
{ // this block is run 40 times }
使用 Int的重要扩展 ...
40.times
{ // this block is run 40 times }
推荐答案
在Swift中没有预处理器宏,但是您可以使用迭代计数和闭包作为参数来定义全局 function :
There are no preprocessor macros in Swift, but you can define a global function taking the iteration count and a closure as arguments:
func forCount(count : Int, @noescape block : () -> ()) {
for _ in 0 ..< count {
block()
}
}
使用尾随闭包语法",它看起来像内置 控制语句:
With the "trailing closure syntax", it looks like a built-in control statement:
forCount(40) {
print("*")
}
@noescape
属性允许编译进行一些优化
并在不使用self
的情况下引用实例变量,请参见
Swift 1.2中的@noescape属性以获取更多信息.
The @noescape
attribute allows the compile to make some optimizations
and to refer to instance variables without using self
, see
@noescape attribute in Swift 1.2 for more information.
自 Swift 3起,"noescape"是该功能的默认属性 参数:
As of Swift 3, "noescape" is the default attribute for function parameters:
func forCount(_ count: Int, block: () -> ()) {
for _ in 0 ..< count {
block()
}
}
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