NSURLWeirdness.m

//
//  main.m
//  NSURLWeirdness
//
//  Created by Andrew Kehrig on 6/24/16.
//  Copyright © 2016 dudid llc. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface NSURL (BetterRelativeToURLSupport)
+(instancetype)betterURLWithString:(NSString*)relativeString relativeToURL:(NSURL*)baseURL;
@end
@implementation NSURL (BetterRelativeToURLSupport)
+(instancetype)betterURLWithString:(NSString*)relativeString relativeToURL:(NSURL*)baseURL
{
    //It's called 'relativeToURL' for a reason right? Even if this baseURL doesn't end in a /
    //we should fix it because the developer said this is the base URL so the entire URL 
    //should be treated as the base.
    if ([baseURL.absoluteString characterAtIndex:(baseURL.absoluteString.length - 1)] != '/' ) {
        baseURL = [NSURL URLWithString:[baseURL.absoluteString stringByAppendingString:@"/"]];
    }
    
    //So this is an interesting part.
    //The only requirements are that the string conform to RFC2396, that it not be nil, 
    //and that it will be interpreted relative to the baseURL. So why, if the baseURL 
    //has additional path components, do we nix those and interpret it, in a more absolute 
    //style? We probably shouldn't - the user asked for a baseURL with additional path
    //components, so if they exist, we should interpret the relativeString relative 
    //with the entire baseURL and all included path components.
    if ([baseURL pathComponents].count > 1 && [relativeString characterAtIndex:0] == '/') {
        relativeString = [@"." stringByAppendingString:relativeString];
    }
    return [NSURL URLWithString:relativeString relativeToURL:baseURL];
}
@end


int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSString *basePath = @"https://some.awesome.host.com:9999/api/v1";
        NSString *relativePath = @"/account/user/1";
        NSURL *baseURL = [NSURL URLWithString:basePath];
        NSURL *unexpectedURL = [NSURL URLWithString:relativePath relativeToURL:baseURL];
        
        NSRange range = NSMakeRange(0, 1);
        NSString *moreRelativePath = [relativePath stringByReplacingCharactersInRange:range withString:@"./"];
        NSURL *potentiallyExpectedURL = [NSURL URLWithString:moreRelativePath relativeToURL:baseURL];
        
        NSLog(@"\n---------\n\nunexpected URL absoluteString: %@\n", unexpectedURL.absoluteString);
        NSLog(@"potentially \"expected\" URL absoluteString: %@\n", potentiallyExpectedURL.absoluteString);
        NSLog(@"expected URL absoluteString: %@\n", [NSURL betterURLWithString:relativePath relativeToURL:baseURL].absoluteString);
        
        /** example output
        ---------
        
        unexpected URL absoluteString: https://some.awesome.host.com:9999/account/user/1
        2016-06-24 02:28:09.283 NSURLBugXcode7[29155:385606] potentially "expected" URL absoluteString: https://some.awesome.host.com:9999/api/account/user/1
        2016-06-24 02:28:09.283 NSURLBugXcode7[29155:385606] expected URL absoluteString: https://some.awesome.host.com:9999/api/v1/account/user/1
        Program ended with exit code: 0
        */
    }
}