How to verify that a given time WebView performs JS-code? - objective-c

Question

This is a Cocoa-component WebView. For example he called JS-function:
[webView stringByEvaluatingJavaScriptFromString:#"foo"];
I need to somehow wait until this function is executed and start doing another job. How this can be done on the Objective-C? I need something like:
[webView waitUntilJavaScriptCodeIsCompleted];

Answer 1

[webView stringByEvaluatingJavaScriptFromString:] is executed synchronously and will return an NSString of the result of executing the passed in script. So, if you just want to know that script has executed, call the function and when it returns, it has executed.
If, however, you're talking about a script with some sort of asynchronous execution, like an XMLHTTPRequest or setTimeout, then you're going to need to have your JavaScript call back into your Objective-C code to let it know when it's finished. Here is an example project that does just that. The most relevant parts are in AppDelegate:
#import "AppDelegate.h"
#import WebKit;
#import JavaScriptCore;
#interface AppDelegate ()
#property (weak) IBOutlet NSWindow *window;
#property (weak) IBOutlet WebView *webView;
#end
#interface AppDelegate (WebDelegate) <WebFrameLoadDelegate>
#end
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
JSGlobalContextRef jsGlobalContext = _webView.mainFrame.globalContext;
// Add a function named "allDone" to the window object. It can be called from JavaScript like so:
JSContext* context = [JSContext contextWithJSGlobalContextRef:jsGlobalContext];
context[#"allDone"] = ^{
NSLog(#"All Done was called");
};
context[#"jsLog"] = ^(NSString* message) {
NSLog(#"JSLOG: %#", message);
};
_webView.frameLoadDelegate = self;
NSURL* url = [NSURL URLWithString:#"https://example.com"];
NSURLRequest *req = [[NSURLRequest alloc] initWithURL:url];
[_webView.mainFrame loadRequest:req];
}
#end
#implementation AppDelegate (WebDelegate)
- (void)webView:(WebView *)sender didFinishLoadForFrame:(WebFrame *)frame {
NSLog(#"Page loaded, calling JavaScript");
// Script that logs a message, and then invokes allDone after 2 seconds.
NSString* script =
#"jsLog('Script running');"
#"setTimeout(function() {\n"
#"jsLog('javascript timer fired, invoking allDone...');\n"
#"window.allDone();\n"
#"}, 2000);";
NSLog(#"Before stringByEvaluatingJavaScriptFromString");
[_webView stringByEvaluatingJavaScriptFromString:script];
NSLog(#"After stringByEvaluatingJavaScriptFromString");
}
#end
Which results in the following output:
Page loaded, calling JavaScript
Before stringByEvaluatingJavaScriptFromString
JSLOG: Script running
After stringByEvaluatingJavaScriptFromString
JSLOG: javascript timer fired, invoking allDone...
All Done was called