Massively Confused About Query Strings

Question

I am using AlamoFire to make an API request. Connecting to the API has been pretty straight forward, what has been massively challenging is querying the API.

I am attempting to create a query string similar to this:

https://api-fxtrade.oanda.com/v3/instruments/USD_CAD/candles?price=BA&from=2016-10-17T15%3A00%3A00.000000000Z&granularity=M1

I feel like I have explored a lot of the internet for documentation on the subject and have come up short..

Does anyone have any resources or advice to share about query strings?

Answer 1

The easiest way to make a query string is to use URLComponents, which handles all the percentage escape for you:

// Keep the init simple, something that you can be sure won't fail
var components = URLComponents(string: "https://api-fxtrade.oanda.com")!

// Now add the other items to your URL query
components.path = "/v3/instruments/USD_CAD/candles"
components.queryItems = [
    URLQueryItem(name: "price", value: "BA"),
    URLQueryItem(name: "from", value: "2016-10-17T15:00:00.000000000Z"),
    URLQueryItem(name: "granularity", value: "M1")
]

if let url = components.url {
    print(url)
} else {
    print("can't make URL")
}

That is with pure Swift, which you should familiarize yourself with. Once you have master the basics, Alamofire can simplify it for you:

let params = [
    "price": "BA",
    "from": "2016-10-17T15:00:00.000000000Z",
    "granularity": "M1"
]
Alamofire.request("https://api-fxtrade.oanda.com/v3/instruments/USD_CAD/candles", parameters: params)
    .responseData { response in
        // Handle response
    }