You are using UIWebView in your iOS app and you want to do some communications between the Javascript inside the WebView and Objective-C. How would you do it?

To run Javascript in Objective-C, you can use the – stringByEvaluatingJavaScriptFromString: method. To run Objective-C method, well it is a little bit tricky, you need to implement the UIWebViewDelegate and the shouldStartLoadWithRequest method.

Do you know how to do this in Android? You simply need to create a class and pass an instance to the WebView through addJavascriptInterface(Object object, String name).

EasyJSWebView is a library that allows you to do the same in Objective-C. Download it and try. I promise. It is much simpler to do the job!!!

You may find the sample project here.

###Some code to demonstrate So basically what you need to do is create a class like this.

@interface MyJSInterface : NSObject

- (void) test;
- (void) testWithParam: (NSString*) param;
- (void) testWithTwoParam: (NSString*) param AndParam2: (NSString*) param2;

- (NSString*) testWithRet;

@end

Then add the interface to your UIWebView.

MyJSInterface* interface = [MyJSInterface new];
[self.myWebView addJavascriptInterfaces:interface WithName:@"MyJSTest"];
[interface release];

In Javascript, you can call the Objective-C methods by this simple code.

MyJSTest.test();
MyJSTest.testWithParam("ha:ha");
MyJSTest.testWithTwoParamAndParam2("haha1", "haha2");

var str = MyJSTest.testWithRet();

Just that simple!!! EasyJSWebView will help you do the injection. And you do not even need to use async-style writing to get the return value!!!

But of course, sometimes we may need to use the async-style code. It is also supported. You can even get the return value from the callback function.

- (void) testWithFuncParam: (EasyJSDataFunction*) param{
  NSLog(@"test with func");
	
	NSString* ret = [param executeWithParam:@"blabla:\"bla"];
	
	NSLog(@"Return value from callback: %@", ret);
}

And in Javascript,

MyJSTest.testWithFuncParam(function (data){
	alert(data); //data would be blabla:"bla
	return "some data";
});

Simple, huh!?

Try it now!!!

###Some simple facts

• NSInvocation does not live peacefully with ARC. This library is thus a non-ARC library.
• It supports only NSString* for message passing now.
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