Check if an URL has got http:// prefix

问题:

In my application, when the user add an object, can also add a link for this object and then the link can be opened in a webView.
I tried to save a link without http:// prefix, then open it in the webView but that can't open it!
Before webView starts loading, is there a method to check if the URL saved has got http:// prefix? And if it hasn't got it, how can I add the prefix to the URL?
Thanks!

回答1:

You can use the - (BOOL)hasPrefix:(NSString *)aString method on NSString to see if an NSString containing your URL starts with the http:// prefix, and if not add the prefix.

NSString *myURLString = @"www.google.com";
NSURL *myURL;
if ([myURLString.lowercaseString hasPrefix:@"http://"]) {
    myURL = [NSURL URLWithString:myURLString];
} else {
    myURL = [NSURL URLWithString:[NSString stringWithFormat:@"http://%@",myURLString]];
}

I'm currently away from my mac and can't compile/test this code, but I believe the above should work.

回答2:

NSString * urlString = ...;
NSURL * url = [NSURL URLWithString:urlString];
if (![[url scheme] length])
{
  url = [NSURL URLWithString:[@"http://" stringByAppendingString:urlString]];
}

回答3:

I wrote an extension for String in Swift, to see if url string got http or https

extension String{

    func isValidForUrl()->Bool{

        if(self.hasPrefix("http") || self.hasPrefix("https")){
            return true
        }
        return false
    }
}

if(urlString.isValidForUrl())
    {
      //Do the thing here.
}

回答4:

I am not sure if there is any method to check that but you check it in the code.

try using

NSRange range = [urlString rangeOfString:@"http://"];
if (range.location != NSNotFound)
    // Add http://  

回答5:

Better to use the scheme property on the URL object:

extension URL {
    var isHTTPScheme: Bool {
        return scheme?.contains("http") == true // or hasPrefix
    }
}

Example usage:

let myURL = https://stackoverflow.com/a/48835119/1032372
if myURL.isHTTPScheme {
    // handle, e.g. open in-app browser:            
    present(SFSafariViewController(url: url), animated: true)
} else if UIApplication.shared.canOpenURL(myURL) {
    UIApplication.shared.openURL(myURL)
}

回答6:

If you're checking for "http://" you'll probably want case-insensitive search:

// probably better to check for just http instead of http://
NSRange prefixRange = 
    [temp rangeOfString:@"http" 
                options:(NSAnchoredSearch | NSCaseInsensitiveSearch)];
if (prefixRange.location == NSNotFound)

Although I think the url scheme check is a better answer depending on your circumstances, as URLs can begin with http or https and other prefixes depending on what your use case is.

回答7:

First, you should create a new category for NSURL: File > New File > Objective-C Category. You can call the category something along the lines of HTTPURLWithString, make it a category of NSURL, press next and add it to your target. Then in the NSURL+HTTPURLFromString.m implement the following message (and declare the message in your .h)

@implementation NSURL (HTTPURLFromString)
+(NSURL *)HTTPURLFromString:(NSString *)string
{
    NSString *searchString = @"http";
    NSRange prefixRange = [string rangeOfString:searchString options:(NSCaseInsensitiveSearch | NSAnchoredSearch)];

    if (prefixRange.length == 4) {
        return [NSURL URLWithString:string];
    }
    return [NSURL URLWithString:[NSString stringWithFormat:@"http://%@", string]];

}
@end

To open a link in the WebView is simply

NSString *urlString = @"www.google.com";
NSURL *url = [NSURL HTTPURLFromString:urlString];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[webView.mainFrame loadRequest:request];

回答8:

You can use scheme property for check it out. For example...

if ([yourURL.scheme isEqualToString:@"http"] || [yourURL.scheme isEqualToString:@"https"]) {
    ...
}