将可选的回调传递给Swift函数 [英] Passing optional callback into Swift function
问题描述
我正在学习Swift lang,但是我无法将可选的回调参数传递给函数:
func dismiss(completion: ) - > Void){
if(completion){
return self.dismissViewControllerAnimated(true,completion:completion)
}
self.dismissModalViewControllerAnimated(true)
}
这给我一个错误 - Type() - >无效符合协议'LogicValue'
有什么建议?
更新Swift 3/4:
可选不再是布尔表达式,
弃用 func dismissModalViewControllerAnimated(animated:Bool)
在Swift中不再可用。
简单地将完成参数声明为可选闭包,并且
将它传递给
func dismiss(animated flag:Bool ,完成:(() - > Void)?= nil)
well:
func dismiss(completion:(() - > Void)?= nil){
self。 dismiss(animated:true,completion:completion)
}
Old(Swift 1.x?)答案:
声明完成
参数为(隐式解包)可选 c losure (() - > () - > Void)!
:
func dismiss {
if(completion){
return self.dismissViewControllerAnimated(true,completion:completion)
}
self.dismissModalViewControllerAnimated(true)
}
但请注意,您可以调用
self.dismissViewControllerAnimated(true,completion:completion)
无论如何,因为<该函数的code> completion 参数也是可选的。
和
func dismissModalViewControllerAnimated(animated:Bool)
实际上标记为弃用。
I'm learning Swift lang, but I cannot pass optional callback argument into function:
func dismiss(completion: () -> Void) {
if (completion) {
return self.dismissViewControllerAnimated(true, completion: completion)
}
self.dismissModalViewControllerAnimated(true)
}
This shows me an error - Type () -> Void does not conform to protocol 'LogicValue'
Any suggestions?
Update for Swift 3/4:
An optional is no longer a boolean expression, and the
deprecated func dismissModalViewControllerAnimated(animated: Bool)
is no longer available in Swift.
Simply declare the completion parameter as an optional closure, and pass it on to
func dismiss(animated flag: Bool, completion: (() -> Void)? = nil)
which takes an optional closure as well:
func dismiss(completion: (() -> Void)? = nil) {
self.dismiss(animated: true, completion: completion)
}
Old (Swift 1.x?) answer:
Declare the completion
parameter as (implicitly unwrapped) optional closure (() -> Void)!
:
func dismiss(completion: (() -> Void)!) {
if (completion) {
return self.dismissViewControllerAnimated(true, completion: completion)
}
self.dismissModalViewControllerAnimated(true)
}
But note that you can call
self.dismissViewControllerAnimated(true, completion: completion)
in any case, because the completion
parameter of that function is optional as well.
And
func dismissModalViewControllerAnimated(animated: Bool)
is actually marked as deprecated.
这篇关于将可选的回调传递给Swift函数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!