Convert Dictionary to Query String in Swift

Convert dictionary to query string in swift?

var populatedDictionary = ["key1": "value1", "key2": "value2"]

extension Dictionary {
    var queryString: String {
        var output: String = ""
        for (key,value) in self {
            output +=  "\(key)=\(value)&"
        }
        output = String(output.characters.dropLast())
        return output
    }
}

print(populatedDictionary.queryString)

// Output : key1=value1&key2=value2

Hope it helps. Happy Coding!!

How do I convert url.query to a dictionary in Swift?

Simple Extension

extension URL {
    var queryDictionary: [String: String]? {
        guard let query = self.query else { return nil}

        var queryStrings = [String: String]()
        for pair in query.components(separatedBy: "&") {

            let key = pair.components(separatedBy: "=")[0]

            let value = pair
                .components(separatedBy:"=")[1]
                .replacingOccurrences(of: "+", with: " ")
                .removingPercentEncoding ?? ""

            queryStrings[key] = value
        }
        return queryStrings
    }
}

USAGE

let urlString = "http://www.youtube.com/video/4bL4FI1Gz6s?hl=it_IT&iv_logging_level=3&ad_flags=0&endscreen_module=http://s.ytimg.com/yt/swfbin/endscreen-vfl6o3XZn.swf&cid=241&cust_gender=1&avg_rating=4.82280613104"
let url = URL(string: urlString)
print(url!.queryDictionary ?? "NONE")

How to build a URL by using Dictionary in Swift

Here is a code snippet to convert dictionary to URLQueryItems:

let dictionary = [
    "name": "Alice",
    "age": "13"
]

func queryItems(dictionary: [String:String]) -> [URLQueryItem] {
    return dictionary.map {
        // Swift 3
        // URLQueryItem(name: $0, value: $1)

        // Swift 4
        URLQueryItem(name: $0.0, value: $0.1)
    }
}

var components = URLComponents()
components.queryItems = queryItems(dictionary: dictionary)
print(components.url!)

Encode url string to Dictionary In my case: Some value have = inside

Piggyback on URLComponents:

var components = URLComponents()
components.query = "id=sfghsgh=sbfsfhj&name=awsjdk_fs"

components.queryItems
// => Optional([id=sfghsgh=sbfsfhj, name=awsjdk_fs])

let list = components.queryItems?.map { ($0.name, $0.value) } ?? []
// [("id", Optional("sfghsgh=sbfsfhj")), ("name", Optional("awsjdk_fs"))]

let dict = Dictionary(list, uniquingKeysWith: { a, b in b })
// ["name": Optional("awsjdk_fs"), "id": Optional("sfghsgh=sbfsfhj")]

If you need a [String: String] rather than [String: String?]:

let list = components.queryItems?.compactMap { ($0.name, $0.value) as? (String, String) } ?? []
// [("id", "sfghsgh=sbfsfhj"), ("name", "awsjdk_fs")]

let dict = Dictionary(list, uniquingKeysWith: { a, b in b })
// ["name": "awsjdk_fs", "id": "sfghsgh=sbfsfhj"]

Convert nested dictionary to create String Swift

With:

struct Item {
    let name: String?
    let itemId: String?
}

let dict: [String: [Item]] = ["price": [Item(name: "10-25", itemId: "10-25")],
                              "publisher": [Item(name: "ABCD", itemId: "576"),
                                            Item(name: "DEFG", itemId: "925"),
                                            Item(name: "HIJK", itemId: "1737")]]

You could use:

var keys = ["price", "publisher"]
let reduced = keys.reduce(into: [String]()) { result, current in
    guard let items = dict[current] else { return }
    let itemsStr = items.compactMap {$0.itemId }.joined(separator: ",")
    result.append("\(current):\(itemsStr)")
}
let finalStr = reduced.joined(separator: ";")
print(finalStr)

The idea:
Iterate over the needed keys (and order guaranteed), construct for each keys, the itemsIds list joined by "," and then append that with the key.
Finally, joined all that.

Add-on questions:
Why is name and itemId optional? Is that normal?

Site note: giving the first part (easily reproducible input) can increase the change of answers, so we don't have to recreate ourselves fake data to check our answers.

Convert a Dictionary to string of url parameters?

One approach would be:

var url = string.Format("http://www.yoursite.com?{0}",
    HttpUtility.UrlEncode(string.Join("&",
        parameters.Select(kvp =>
            string.Format("{0}={1}", kvp.Key, kvp.Value)))));

You could also use string interpolation as introduced in C#6:

var url = $"http://www.yoursite.com?{HttpUtility.UrlEncode(string.Join("&", parameters.Select(kvp => $"{kvp.Key}={kvp.Value}")))}";

And you could get rid of the UrlEncode if you don't need it, I just added it for completeness.

Best way to parse URL string to get values for keys?

edit (June 2018): this answer is better. Apple added NSURLComponents in iOS 7.

I would create a dictionary, get an array of the key/value pairs with

NSMutableDictionary *queryStringDictionary = [[NSMutableDictionary alloc] init];
NSArray *urlComponents = [urlString componentsSeparatedByString:@"&"];

Then populate the dictionary :

for (NSString *keyValuePair in urlComponents)
{
    NSArray *pairComponents = [keyValuePair componentsSeparatedByString:@"="];
    NSString *key = [[pairComponents firstObject] stringByRemovingPercentEncoding];
    NSString *value = [[pairComponents lastObject] stringByRemovingPercentEncoding];

    [queryStringDictionary setObject:value forKey:key];
}

You can then query with

[queryStringDictionary objectForKey:@"ad_eurl"];

This is untested, and you should probably do some more error tests.

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