如何将 Objective-C 值传递给 JavaScript

Question

Now I would like to pass an Objective-C object (String) to JavaScript (in WKWebView).

Want to load an Objective-C variable into JavaScript at the timing when window.onload is executed, as shown below.

var objcString = "";

window.onload = function() {
    objcString = objc.getObjcString();

    execXxxWhenWindowOnload(objcString);
}

How can I implement Objective-C function?

Answer 1

you can use evaluateJavaScript function for passing value. Here is an example of it please check

- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation {
  NSString *strFunction = [NSString stringWithFormat:@"'function name'('%@')",'value'];
  [self.webview evaluateJavaScript:strFunction completionHandler:nil];
}

Answer 2

Assuming:

• it's a URL request you initiate from the app that will land you on the page(opposed to navigating to some link later on)
• you don't want to pass sensitive data

you could consider using a query param (albeit be wary not to clash with some existing query param names in the url).

NSString *yourCustomString = @"value";
NSString *urlString = [NSString stringWithFormat:@"https://www.yourserver.com?myParam=%@", yourCustomString];
[self.webView loadRequest:[NSURLRequest requestWithURL: [NSURL URLWithString:urlString]]];

In the js counterpart you'd handle that like this:

window.onload = function() {
    const urlParams = new URLSearchParams(window.location.search);
    const myParam = urlParams.get('myParam');
    execXxxWhenWindowOnload(myParam);
}

I haven't found a way to inject custom js before window.onload using WKUserScript / WKUserScriptInjectionTimeAtDocumentStart duo.