从Objective-C在iOS Web应用程序中调用Javascript

Question

I am developing a web app that is being displayed in a UIWebView . The app is loaded locally, ie, not from a web server. I am communicating from Javascript to ObjC via the shouldStartLoadWithRequest: method in the UIWebViewDelegate protocol.

The last thing I need is to be able to call Javascript functions from ObjC without any page reloads. I hope this is possible.

Answer 1

Well, you can call

-[UIWebView stringByEvaluatingJavaScriptFromString:]

whenever you like, not just in response to a delegate method.

Answer 2

You can call any javascript function in your webview by simply using the stringByEvaluatingJavaScriptFromString method on your webview after you've loaded the webview:

[self.myWebView stringByEvaluatingJavaScriptFromString:@"myJavaScriptFunction(123.0)"];

You don't need to reload the webview to send this message (just don't release the webview before you're done).

Answer 3

Could't you just do this by doing a "loadRequest", and passing it an NSURL with contents like like:

javascript:myFunction("MyParameter");

It should call your function, but not reload the page.

Answer 4

One can use JavaScriptCore framework to run JavaScript code from Objective-C.

#import <JavaScriptCore/JavaScriptCore.h>

...

JSContext *context = [[JSContext alloc] init];
[context evaluateScript: @"function greet(name){ return 'Hello, ' + name; }"];
JSValue *function = context[@"greet"];
JSValue* result = [function callWithArguments:@[@"World"]];
[result toString]; // -> Hello, World

Here is a demo:

https://github.com/evgenyneu/ios-javascriptcore-demo