如何将JavaScript回调函数传递给Cocoa / Obj-C？

问题描述

我正在尝试从WebView中的JavaScript传递函数引用，因此异步Obj-C方法完成后，我的Objective-C代码可以调用然后再返回该函数。我看到了如何传递简单的类型-字符串，数字等-但似乎无法弄清楚如何传递函数引用，例如

I'm trying to pass a function reference from JavaScript in a WebView, so my Objective-C code can call then back into that function when the asynchronous Obj-C method completes. I see how to pass in simple types -- strings, numbers, etc. -- but can't seem to figure out how to pass something a function reference, like

window.myRootObject.myObjCSelector("some-string", function(data) {
  console.log(data);
});

我已经在Google周围搜索，但仍然很简短，并且没有找到在文档中（尚未）。在Cocoa工作，但希望能够在iOS上做同样的事情。

I've Googled around, but continue to come up short, and haven't found a reference to this in the docs (yet). Working in Cocoa, but would love to be able to do the same sort of thing on iOS.

在此先感谢您的帮助！

编辑：函数参数应该是匿名的-希望可以弄清楚。 ：）

The function argument should be anonymous -- hopefully this clarifies. :)

推荐答案

最后弄清楚了这一点。也许有更好的方法（如果是，请发出提示！），但以下方法似乎可行。在我的Obj-C（ NSObject 派生）类中-向其中传递对 WebView 的引用-我定义了以下脚本可访问的方法：

Finally figured this out. There might be a better way (and if so, please chime in!) but the following seems to work. In my Obj-C (NSObject-derived) class -- into which I pass a reference to a WebView -- I define the following script-accessible method:

#import <WebKit/WebKit.h>
#import <JavaScriptCore/JavaScriptCore.h>

- (void) search:(NSString *)prefix withCallback:(WebScriptObject *)callback;

...旨在接受两个参数：一个用于搜索的字符串和一个匿名函数回调以处理结果。它是这样实现的：

... which is intended to take two arguments: a string to search with, and an anonymous function callback to handle the result. It's implemented thusly:

- (void) search:(NSString *)prefix withCallback:(WebScriptObject *)callback
{
  // Functions get passed in as WebScriptObjects, which give you access to the function as a JSObject
  JSObjectRef ref = [callback JSObject];

  // Through WebView, you can get to the JS globalContext
  JSContextRef ctx = [[view mainFrame] globalContext];

  // In my case, I have a JSON string I want to pass back into the page as a JavaScript object
  JSValueRef obj = JSValueMakeFromJSONString(ctx, JSStringCreateWithCFString((__bridge CFStringRef)responseString));

  // And here's where I call the callback and pass in the JS object
  JSObjectCallAsFunction(ctx, ref, NULL, 1, &obj, NULL);
}

实际上，它也可以通过Objective-C块异步运行，但是要点以上。希望它对其他人有帮助！

This actually works asynchronously as well, through Objective-C blocks, but the gist is above. Hope it helps someone else!

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