Objective C Macos Cocoa

Opening Non-Standard URLs in a Cocoa App

When developing a Cocoa application, you may encounter the need to open URLs that are not properly formatted. This can lead to issues when trying to utilize the openURL method to launch your intended webpage or resource. In this blog post, we will address a common problem related to opening non-standard URLs in Cocoa apps and explain how you can effectively handle them.

The Problem

Imagine you are working on an application where you need to open a specific URL. Your code may look something like this:

NSWorkspace* ws = [NSWorkspace sharedWorkspace];
NSString* myurl = @"http://www.somewebsite.com/method?a=%d";

NSURL* url = [NSURL URLWithString:myurl];

[ws openURL:url];

This code snippets shows that your URL contains a placeholder (%d) that is not properly formatted. When you attempt to create an NSURL object with this string, it results in nil because the URL is invalid.

Why Does This Happen?

The NSURL class requires a correctly formatted URL, and the presence of the placeholder (%) causes it to fail. If you receive this URL from an external source, it is important to handle it properly before attempting to use it in your application.

The Solution

To solve the issue of improperly formatted URLs, you can use a built-in method from the NSString class. This method will sanitize your URL so that it can be opened without errors. The method to use is stringByAddingPercentEscapesUsingEncoding:.

Step-by-Step Guide

  1. Sanitize the URL: First, you need to replace the invalid parts of the URL string with valid percent escapes. This ensures that any special characters, including placeholders, are properly encoded.

  2. Create the NSURL Object: Once the string is sanitized, you can then create a valid NSURL object.

  3. Open the URL: Finally, use the NSWorkspace to open the sanitized URL.

Example Code

Here’s how you would implement this in your code:

// Step 1: Sanitize the URL
NSString *myurl = @"http://www.somewebsite.com/method?a=%d";
NSString *sanitizedURL = [myurl stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

// Step 2: Create a NSURL object
NSURL *url = [NSURL URLWithString:sanitizedURL];

// Step 3: Open the URL
NSWorkspace *ws = [NSWorkspace sharedWorkspace];
[ws openURL:url];

Important Notes

  • Deprecation Warning: Please note that stringByAddingPercentEscapesUsingEncoding: is deprecated in newer versions of macOS. It is recommended to use stringByAddingPercentEncodingWithAllowedCharacters: for modern development.
  • Always ensure that the input URL is safe to avoid security vulnerabilities, especially if the URL comes from an untrusted source.

Conclusion

Opening a non-standard URL in a Cocoa app may seem challenging initially, but with the proper sanitization methods, you can handle these situations effectively. By utilizing the stringByAddingPercentEscapesUsingEncoding: method (or its more modern equivalent), you will ensure that your application can seamlessly open URLs, enhancing the user experience and maintaining functionality.

Now that you know how to handle non-standard URLs, implement this solution in your Cocoa app and enjoy smooth navigation!