Xcode iPhone HOW do I interact with a web page that has alreaded loaded?

In viewDidLoad I have

[webView loadRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"https://w开发者_JAVA百科ebpage_etc"]]];

which loads the web page fine, but this web page has a name, password and submit button. How do I fill in (with Xcode) the name password and hit the submit button.

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Use stringByEvaluatingJavaScriptFromString: to inject some javascript that manipulates the objects in the page.