Creating URL query parameters from NSDictionary objects in ObjectiveC

Admin 1
Viewed 74472

With all the URL-handling objects lying around in the standard Cocoa libraries (NSURL, NSMutableURL, NSMutableURLRequest, etc), I know I must be overlooking an easy way to programmatically compose a GET request.

Currently I'm manually appending "?" followed by name value pairs joined by "&", but all of my name and value pairs need to be manually encoded so NSMutableURLRequest doesn't fail entirely when it tries to connect to the URL.

This feels like something I should be able to use a pre-baked API for.... is there anything out of the box to append an NSDictionary of query parameters to an NSURL? Is there another way I should approach this?

nsurl objective-c
13 Answers

You can create a category for NSDictionary to do this -- there isn't a standard way in the Cocoa library that I could find either. The code that I use looks like this:

// file "NSDictionary+UrlEncoding.h"
#import <cocoa/cocoa.h>

@interface NSDictionary (UrlEncoding)

-(NSString*) urlEncodedString;

@end

with this implementation:

// file "NSDictionary+UrlEncoding.m"
#import "NSDictionary+UrlEncoding.h"

// helper function: get the string form of any object
static NSString *toString(id object) {
  return [NSString stringWithFormat: @"%@", object];
}

// helper function: get the url encoded string form of any object
static NSString *urlEncode(id object) {
  NSString *string = toString(object);
  return [string stringByAddingPercentEscapesUsingEncoding: NSUTF8StringEncoding];
}

@implementation NSDictionary (UrlEncoding)

-(NSString*) urlEncodedString {
  NSMutableArray *parts = [NSMutableArray array];
  for (id key in self) {
    id value = [self objectForKey: key];
    NSString *part = [NSString stringWithFormat: @"%@=%@", urlEncode(key), urlEncode(value)];
    [parts addObject: part];
  }
  return [parts componentsJoinedByString: @"&"];
}

@end

I think the code's pretty straightforward, but I discuss it in some more detail at http://blog.ablepear.com/2008/12/urlencoding-category-for-nsdictionary.html.

Don_McCaughey_657640

I took Joel's recommendation of using URLQueryItems and turned into a Swift Extension (Swift 3)

extension URL
{
    /// Creates an NSURL with url-encoded parameters.
    init?(string : String, parameters : [String : String])
    {
        guard var components = URLComponents(string: string) else { return nil }

        components.queryItems = parameters.map { return URLQueryItem(name: $0, value: $1) }

        guard let url = components.url else { return nil }

        // Kinda redundant, but we need to call init.
        self.init(string: url.absoluteString)
    }
}

(The self.init method is kinda cheesy, but there was no NSURL init with components)

Can be used as

URL(string: "http://www.google.com/", parameters: ["q" : "search me"])
user_8686940

If you are already using AFNetwork, you can use their built in serializer to to produce an encoded URL;

NSString *baseURL = @"https://api.app.com/parse";
NSDictionary *mutableParameters = [[NSMutableDictionary alloc] initWithObjectsAndKeys:@"true",@"option1", data, @"option2", token, @"token", @"3.0", @"app", nil];
NSURLRequest *request = [[AFHTTPRequestSerializer serializer] requestWithMethod:@"GET" URLString:baseURL parameters:mutableParameters error:nil];
NSString *urlPath = request.URL.absoluteString;
NSLog(@"%@", urlPath); // https://api.app.com/parse?option1=true&option2=datavalue&token=200%3ATEST%3AENCODE ....

Note; this is an extension to an above answer. The edit queue is full so cannot be added to the existing answer.

user_13492170
Related