Back Button on UIWebView

actionSheet:clickedButtonAtIndex: is for UIActionSheet objects, not UIButton actions.

You should probably write an IBAction method that looks something like this:

- (IBAction)backButtonTapped:(id)sender {
   [_viewWeb goBack];
}

and connect it to the Touch Up Inside action from the button.

You can search for more info on IBAction but that's likely what you want

For swift 4 and swift 5

@IBAction func refreshAction(_ sender: Any) {
    self.webView.reload()
}

@IBAction func backAction(_ sender: Any) {
    if(self.webView.canGoBack) {
        self.webView.goBack()
       }
}

@IBAction func forwardAction(_ sender: Any) {
    if self.webView.canGoForward{
        self.webView.goForward()
    }
}