Swift stringByEvaluatingJavaScriptFromString [英] Swift stringByEvaluatingJavaScriptFromString

问题描述

我尝试在我的WebView上使用一些新的

I try to use some javascript on my WebView with the new

stringByEvaluatingJavaScriptFromString function

stringByEvaluatingJavaScriptFromString function

我不熟悉语法，所以我试过

I m not quiet familiar with the syntax so i tried

 func stringByEvaluatingJavaScriptFromString( "document.documentElement.style.webkitUserSelect='none'": String) -> String? 

如此处所示 https://developer.apple.com/library/ios/documentation/UIKit/Reference /UIWebView_Class/index.html#//apple_ref/occ/instm/UIWebView/stringByEvaluatingJavaScriptFromString ：但是我收到一个错误Expected'。'separator

as shown here https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIWebView_Class/index.html#//apple_ref/occ/instm/UIWebView/stringByEvaluatingJavaScriptFromString: but i get a error that "Expected '.' separator"

推荐答案

您尝试调用的方法原型如下：

The method you are trying to call is prototyped as the following:

func stringByEvaluatingJavaScriptFromString（_ script ：String） - >字符串？

这意味着：

• 它将 String 作为单个参数


• 它返回一个可选的字符串（ String？）

• It takes a String as single parameter
• It returns an optional String (String?)

你需要一个 UIWebView 使用它：

let result = webView.stringByEvaluatingJavaScriptFromString("document.documentElement.style.webkitUserSelect='none'")

因为返回类型是可选 ，它需要在你可以使用它之前解开。
但要小心，它可能没有值（即它可能等于 nil ）并且解包nil值会导致运行时崩溃。

Because the return type is optional, it needs to be unwrapped before you can use it. But be careful, it may not have a value (i.e. it may be equal to nil) and unwrapping nil values leads to runtime crashes.

所以你需要在使用返回的字符串之前检查一下：

So you need to check for that before you can use the returned string:

if let returnedString = result {
    println("the result is \(returnedString)")
}

这意味着：如果结果不是 nil 然后打开它并将其分配给新的常量名为 returnedString 。

This means: If result is not nil then unwrap it and assign it to a new constant called returnedString.

此外，你可以将它包装在一起：

Additionally, you can wrap it together with:

let script = "document.documentElement.style.webkitUserSelect='none'"
if let returnedString = webView.stringByEvaluatingJavaScriptFromString(script) {
    println("the result is \(returnedString)")
}

希望这对你有意义。

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