How can I build a URL with query parameters containing multiple values for the same key in Swift?

Question

I am using AFNetworking in my iOS app and for all the GET requests it makes, I build the url from a base URL and than add parameters using NSDictionary Key-Value pairs.

The problem is that I need same key for different values.

Here is an example of what I need the finally URL to look like -

http://example.com/.....&id=21212&id=21212&id=33232

It's not possible in NSDictionary to have different values in same keys. So I tried NSSet but did not work.

let productIDSet: Set = [prodIDArray]
let paramDict = NSMutableDictionary()
paramDict.setObject(productIDSet, forKey: "id")

Daniel Galasko · Accepted Answer · 2020-04-14T10:39:39.550

182

All you need is URLComponents (or NSURLComponents in Obj-C). The basic idea is to create a bunch of query items for your id's. Here's code you can paste into a playground:

import Foundation
import XCPlayground

let queryItems = [URLQueryItem(name: "id", value: "1"), URLQueryItem(name: "id", value: "2")]
var urlComps = URLComponents(string: "www.apple.com/help")!
urlComps.queryItems = queryItems
let result = urlComps.url!
print(result)

You should see an output of

www.apple.com/help?id=1&id=2

edited Apr 14 '20 at 10:39

answered Dec 03 '15 at 08:29

Daniel Galasko

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Awesome. Thanks for your answer. I tried looping through and add the value in a for loop as I have my IDs in an array but I am facing a lot of issues. Will you be able to please suggest how do I add values in loop ? Many thanks. – AbhishekDwivedi Dec 03 '15 at 09:08
sure, just make sure you declare your array of `queryItems` as a `var` and then you can add new items in a loop @AbhishekDwivedi – Daniel Galasko Dec 03 '15 at 09:24
Sorry @Daniel to bug you but this is what I am trying to do but not able to. Not sure what the problem is :( var queryItems = [NSURLQueryItem]() let urlComps = NSURLComponents(string: "www.apple.com/help")! for var i = 0 ; i < prodIDArray.count ; i++ { let queryitem = [NSURLQueryItem(name: "id", value: prodIDArray[i] as? String)] queryItems.append(queryitem) } urlComps.queryItems = queryitems – AbhishekDwivedi Dec 03 '15 at 09:59
You don't need to create a query item array in the loop. Just remove the square brackets and you should be good @AbhishekDwivedi – Daniel Galasko Dec 03 '15 at 10:16
My url is like below https://www.abcd.com/json/trend/id/12/key/23456 How can i achieve this ? I am using alamofire 4.0 – Ravi Ojha Mar 10 '17 at 12:11
If anyone get this `Expression type '()' is ambiguous without more context` error, use URLQueryItem instead of NSURLQueryItem – Muhammad Yusuf Apr 08 '20 at 18:12

Bhuvan Bhatt · Answer 2 · 2020-04-20T20:37:35.230

Method 1

It can add the QueryItem to your existing URL.

extension URL {

    func appending(_ queryItem: String, value: String?) -> URL {

        guard var urlComponents = URLComponents(string: absoluteString) else { return absoluteURL }

        // Create array of existing query items
        var queryItems: [URLQueryItem] = urlComponents.queryItems ??  []

        // Create query item
        let queryItem = URLQueryItem(name: queryItem, value: value)

        // Append the new query item in the existing query items array
        queryItems.append(queryItem)

        // Append updated query items array in the url component object
        urlComponents.queryItems = queryItems

        // Returns the url from new url components
        return urlComponents.url!
    }
}

How to use

var url = URL(string: "https://www.example.com")!
let finalURL = url.appending("test", value: "123")
                  .appending("test2", value: nil)

Method 2

In this method, the URL will be updated automatically.

extension URL {

    mutating func appendQueryItem(name: String, value: String?) {

        guard var urlComponents = URLComponents(string: absoluteString) else { return }

        // Create array of existing query items
        var queryItems: [URLQueryItem] = urlComponents.queryItems ??  []

        // Create query item
        let queryItem = URLQueryItem(name: name, value: value)

        // Append the new query item in the existing query items array
        queryItems.append(queryItem)

        // Append updated query items array in the url component object
        urlComponents.queryItems = queryItems

        // Returns the url from new url components
        self = urlComponents.url!
    }
}

// How to use
var url = URL(string: "https://www.example.com")!
url.appendQueryItem(name: "name", value: "bhuvan")

score 12 · Answer 3 · edited Jul 18 '18 at 16:29

12

func queryString(_ value: String, params: [String: String]) -> String? {    
    var components = URLComponents(string: value)
    components?.queryItems = params.map { element in URLQueryItem(name: element.key, value: element.value) }

    return components?.url?.absoluteString
}

edited Jul 18 '18 at 16:29

dimpiax

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answered Mar 23 '18 at 09:47

Kirit Vaghela

12,572
4
76
80

score 10 · Answer 4 · answered Apr 10 '19 at 11:22

An URL extension to append query items, similar to Bhuvan Bhatt idea, but with a different signature:

it can detect failures (by returning nil instead of self), thus allowing custom handling of cases where the URL is not RFC 3986 compliant for instance.
it allows nil values, by actually passing any query items as parameters.
for performance, it allows passing multiple query items at a time.

extension URL {
    /// Returns a new URL by adding the query items, or nil if the URL doesn't support it.
    /// URL must conform to RFC 3986.
    func appending(_ queryItems: [URLQueryItem]) -> URL? {
        guard var urlComponents = URLComponents(url: self, resolvingAgainstBaseURL: true) else {
            // URL is not conforming to RFC 3986 (maybe it is only conforming to RFC 1808, RFC 1738, and RFC 2732)
            return nil
        }
        // append the query items to the existing ones
        urlComponents.queryItems = (urlComponents.queryItems ?? []) + queryItems

        // return the url from new url components
        return urlComponents.url
    }
}

Usage

let url = URL(string: "https://example.com/...")!
let queryItems = [URLQueryItem(name: "id", value: nil),
                  URLQueryItem(name: "id", value: "22"),
                  URLQueryItem(name: "id", value: "33")]
let newUrl = url.appending(queryItems)!
print(newUrl)

Output:

https://example.com/...?id&id=22&id=33

I don't think it is a good idea to allow same key multiple times in a url — atulkhatri, Apr 03 '20 at 08:26
@atulkhatri while the RFC 3986 **allows** it, I'm well aware that, for instance, [on Windows Phone 7/8, the Operating System won't even let you handle URLs with duplicate keys](https://stackoverflow.com/a/26341732/1033581). So I fully agree that it's not the best practice. Consequently its usage will depend on your API. This is [how I filter duplicate keys in Swift](https://stackoverflow.com/a/55684308/1033581): with the code from it, you could add `queryItems.unique(for: \.name)` if you want. — Cœur, Apr 03 '20 at 11:46
I completely understand your intention but I feel being it a front-end code, the app does not know how the server is going to handle it. So in order to be on a safer side, I think it is best to not have such inconsistent query parameters. — atulkhatri, Apr 04 '20 at 11:21

score 7 · Answer 5 · answered Jun 12 '22 at 22:59

7

Update for iOS 16, Swift 5.7+

There's a shorter way available to perform this:

var url = URL(string: "http://google.com/search")
url?.append(queryItems: [URLQueryItem(name: "q", value: "soccer")])
print(url) // http://www.google.com/search?q=soccer

answered Jun 12 '22 at 22:59

Amir.n3t

2,859
3
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1

In iOS 16 there is even the non mutating function `appending`, which *returns* an appended URL. – Jan Mar 01 '23 at 16:58

score 4 · Answer 6 · edited Jun 20 '20 at 09:12

2019

private func tellServerSomething(_ d: String, _ s: String) {
    
    var c = URLComponents(string: "https://you.com/info")
    c?.queryItems = [
        URLQueryItem(name: "description", value: d),
        URLQueryItem(name: "summary", value: s)
    ]
    guard let u = c?.url else { return print("url fail") }
    do {
        let r = try String(contentsOf: u)
        print("Server response \(r)")
    }
    catch { return print("comms fail") }
}

Percent-encoding and everything else is handled.

Wasim · Answer 7 · 2019-05-31T22:27:27.590

1

In Swift Forming URL with multiple params

func rateConversionURL(with array: [String]) -> URL? {
            var components = URLComponents()
            components.scheme = "https"
            components.host = "example.com"
            components.path = "/hello/"
            components.queryItems = array.map { URLQueryItem(name: "value", value: $0)}

        return components.url
    }

edited May 31 '19 at 22:27

answered May 31 '19 at 09:52

Wasim

921
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14

very impressive ! – Fattie Jun 02 '22 at 20:35

score -4 · Answer 8 · answered Dec 03 '15 at 08:23

-4

I guess u just have to do something like this:

let params = ["id" : [1, 2, 3, 4], ...];

which will be encoded into: ....id%5B%5D=1&id%5B%5D=2&id%5B%5D=3&id%5B%5D=4....

answered Dec 03 '15 at 08:23

Serg Dort

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2
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And If you are working with swift I sagest you to use [Alamofire](https://github.com/Alamofire/Alamofire) – Serg Dort Dec 03 '15 at 08:25

How can I build a URL with query parameters containing multiple values for the same key in Swift?

8 Answers8

Method 1

Method 2

Usage

2019

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