Exploring the capabilities of JavaScript on the iOS platform

Here is the code I've written for my iOS application:

webView             =   [[UIWebView alloc] init];
webView.delegate    =   self;

[webView loadHTMLString:@"<script type=\"text/javascript\" src=\"myFile.js\"></script>" baseURL:[NSURL fileURLWithPath:[NSBundle mainBundle].resourcePath]];

NSString* result =(NSString*)[webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"myFunction(%d,%d,%d)", num1,num2,num3]];

NSLog(@"RESULT1 : %@", result);

And this is my JavaScript file, myFile.js:

function myFunction(a,b,c)
{
   return a*b*c;
}

However, I'm not getting any output in the result string. Can someone help me figure out what's wrong?

javascriptios

Answer №1

It is important to wait for the webViewDidFinishLoad: callback after the webview has finished loading.

You can implement the delegate method as shown below:

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSString* result = (NSString*)[webView stringByEvaluatingJavaScriptFromString:[NSString stringWithFormat:@"myFunction(%d,%d,%d)", num1,num2,num3]];
    NSLog(@"RESULT1 : %@", result);
}

Additionally, make sure that your myFile.js is located under the Copy Bundle Resources instead of the Compile Sources section in Target->Build Phases.

If you are not familiar with JavaScript, the syntax for your JS function may appear unusual. The typical syntax is:

function myFunction(a,b,c)
{
   //Check if this alert gets called
   alert('Function called');
   return a*b*c;
}

Please review and verify the syntax.

I hope this information is helpful!

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