[英]Swift execute closure on main thread trough custom operator
Apparently Xcode doesn't let me modify the UI (iOS) from a background thread. 显然,Xcode不允许我从后台线程修改UI(iOS)。 I have to type:
我必须输入:
let res = somethingReturningaString()
dispatch_async(dispatch_get_main_queue(), {
self.txtError.text = res!
})
My idea was: 'hey, let's simplify my life and define a custom operator, so I can type something like:' 我的想法是:“嘿,让我们简化生活并定义一个自定义运算符,这样我就可以输入:
prefix operator ~> {}
prefix func ~> (closure: ()-> ()) {
dispatch_async(dispatch_get_main_queue(), closure)
}
//usage example
~> {self.txtError.text = res!}
Apparently the operator of type '()' cannot be applied to '()->()' Does anybody know how to declare this to get this working? 显然类型'()'的运算符不能应用于'()->()',有人知道如何声明它来使它起作用吗?
The swift compiler got a little confused there. 敏捷的编译器在那里有些困惑。 You must not ever separate a unary operator from its operand, meaning there must not be a whitespace in between.
您绝对不能将一元运算符与其操作数分开,这意味着两者之间一定不能有空格 。
Consider the following example code 考虑以下示例代码
let k = 12
~> {
self.txtError.text = res!
}
Swift now expects ~>
to be a binary operand because there is a whitespace. Swift现在期望
~>
是一个二进制操作数,因为存在空格。
binary operator '~>' cannot be applied to operands of type 'Int' and '() -> ()'
二进制运算符'〜>'不能应用于'Int'和'()->()'类型的操作数
If you insert a ;
如果插入
;
after the first line: 第一行之后:
let k = 12;
~> {
self.txtError.text = res!
}
You receive something a little bit more helpful: 您会得到一些帮助:
Unary operator cannot be separated from its operand
一元运算符不能与其操作数分开
Which simply means that there must in fact be no whitespace. 这仅意味着实际上必须没有空格。
Remove the whitespace: 删除空格:
~>{ self.txtError.text = res! }
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