ios设置userAgent

- (void)setUserAgent{
    __block  NSString *userAgent=@"";
    [self.webView evaluateJavaScript:@"navigator.userAgent" completionHandler:^(id result, NSError *error) {
        userAgent =result;
        NSString *newUserAgent = [userAgent stringByAppendingString:@" ;dzg"];
        self.webView.navigationDelegate = self;
        [self.webView setCustomUserAgent:newUserAgent];
    }];
}