iOS 6+ compatible functions set to update URL parameters

NSURL-Extensions.h

//
//  NSURL-Extensions.h
//  url-modificator
//
//  Created by yury.lapitsky on 26/12/2016.
//  Copyright © 2016 yury.lapitsky. All rights reserved.
//

#import <Foundation/Foundation.h>

#ifndef NSURL_Extensions_h
#define NSURL_Extensions_h

// Assuming that attribute value separator is `=` and pair delimiter is '&'
NSString *buildURLQueryString(NSDictionary *parameters) {
    NSMutableString *query = [NSMutableString new];
    
    for (NSString *key in parameters.allKeys) {
        if (query.length > 0) { [query appendString:@"&"]; }
        
        NSString *value = parameters[key];
        [query appendFormat:@"%@=%@", key, value];
    }
    
    return query.copy;
}

// Assuming that attribute value separator is `=` and pair delimiter is '&'
NSDictionary *parseURLQueryString(NSString *query) {
    NSMutableDictionary *parameters = [NSMutableDictionary dictionary];
    if (query != nil) {
        NSArray *parameterPairs = [query componentsSeparatedByString:@"&"];
        for (NSString *keyValue in parameterPairs) {
            if (keyValue == nil || keyValue.length == 0) { continue; }
            
            NSArray *components = [keyValue componentsSeparatedByString:@"="];
            switch (components.count) {
                case 0: {
                    // only key, no separator and no value.
                    // valid in general terms of URL. To store key in the dictionary set value as an empty string
                    
                    NSString *key = keyValue;
                    parameters[key] = @"";
                    
                    break;
                }
                case 1: {
                    // only key and separator, no value.
                    // valid in general terms of URL. To store key in the dictionary set value as an empty string
                    
                    NSString *key = components.firstObject;
                    parameters[key] = @"";
                    
                    break;
                }
                case 2: {
                    // key and value
                    
                    NSString *key = components[0];
                    NSString *value = components[1];
                    
                    parameters[key] = value;
                    break;
                }
                default: {
                    // invalid parameters pair in the query, skip it
                }
            }
        }
    }
    
    return [NSDictionary dictionaryWithDictionary:parameters];
}


//  Form: scheme:[//[user:password@]host[:port]][/]path[?query][#fragment]
NSURL *replaceQueryInURL(NSURL *url, NSString *query) {
    if (url.absoluteString.length == 0 || query.length == 0) { return url; }
    
    NSMutableString *modifiedURLString = @"".mutableCopy;
    if (url.scheme != nil) {
        [modifiedURLString appendFormat:@"%@://", url.scheme];
    }
    
    if (url.user != nil) {
        [modifiedURLString appendFormat:@"%@", url.user];
        
        if (url.password != nil) {
            [modifiedURLString appendFormat:@":%@", url.password];
        }
    }
    
    if (url.host != nil) {
        [modifiedURLString appendFormat:@"%@", url.host];
        
        if (url.port != nil) {
            [modifiedURLString appendFormat:@"%@", url.port];
        }
    }
    
    if (url.relativePath != nil) {
        modifiedURLString = [modifiedURLString stringByAppendingPathComponent:url.relativePath].mutableCopy;
    }
    
    [modifiedURLString appendFormat:@"?%@", query];
    
    if (url.fragment != nil) {
        [modifiedURLString appendFormat:@"#%@", url.fragment];
    }
    
    return [NSURL URLWithString:modifiedURLString];
}

NSURL *changeURLQueryParams(NSURL *url, void (^block)(NSMutableDictionary *parameters)) {
    if (url.absoluteString.length == 0) { return url; }
    
    NSMutableDictionary *parameters = [NSMutableDictionary dictionary];
    
    NSString *query = url.query;
    if (query != nil) {
        NSDictionary *parsedParameters = parseURLQueryString(query);
        [parameters addEntriesFromDictionary:parsedParameters];
    }
    
    block(parameters);
    
    NSString *modifiedQuery = buildURLQueryString(parameters);
    
    return replaceQueryInURL(url, modifiedQuery);
}

#endif /* NSURL_Extensions_h */