Creating a query string from an NSDictionary.

gistfile1.m

NSDictionary *queryParameters = [NSDictionary dictionaryWithValuesAndKeys:1, @"page", nil, @"enabled", 25, @"size", nil];
[queryParameters queryString]; // This will return "?page=1&enabled&size=25" 

NSDictionary+QueryStringBuilder.h

#import <Foundation/Foundation.h>


@interface NSDictionary (QueryStringBuilder)

- (NSString *)queryString;

@end

NSDictionary+QueryStringBuilder.m

#import "NSDictionary+QueryStringBuilder.h"

static NSString * escapeString(NSString *unencodedString)
{
  NSString *s = (NSString *)CFURLCreateStringByAddingPercentEscapes(NULL,
        (CFStringRef)unencodedString,
        NULL,
        (CFStringRef)@"!*'\"();:@&=+$,/?%#[]% ",
        kCFStringEncodingUTF8);
  return [s autorelease];

}


@implementation NSDictionary (QueryStringBuilder)

- (NSString *)queryString
{
    NSMutableString *queryString = nil;
    NSArray *keys = [self allKeys];
    
    if ([keys count] > 0) {
        for (id key in keys) {
            id value = [self objectForKey:key];
            if (nil == queryString) {
                queryString = [[[NSMutableString alloc] init] autorelease];
                [queryString appendFormat:@"?"];
            } else {
                [queryString appendFormat:@"&"];
            }
            
            if (nil != key && nil != value) {
                [queryString appendFormat:@"%@=%@", escapeString(key), escapeString(value)];
            } else if (nil != key) {
                [queryString appendFormat:@"%@", escapeString(key)];
            }
        }
    }
    
    return queryString;
}

@end