vapor-docs/4.0/docs/content/query.md

Query

Vapor's Content APIs support handling URL encoded data in the URL's query string.

Decoding

To understand how decoding a URL query string works, take a look at the following example request.

GET /hello?name=Vapor HTTP/1.1
content-length: 0

Just like the APIs for handling HTTP message body content, the first step for parsing URL query strings is to create a struct that matches the expected structure.

struct Hello: Content {
	var name: String?
}

Note that name is an optional String since URL query strings should always be optional. If you want to require a parameter, use a route parameter instead.

Now that you have a Content struct for this route's expected query string, you can decode it.

app.get("hello") { req -> String in 
	let hello = try req.query.decode(Hello.self)
	return "Hello, \(hello.name ?? "Anonymous")"
}

This route would result in the following response given the example request from above:

HTTP/1.1 200 OK
content-length: 12

Hello, Vapor

If the query string were omitted, like in the following request, the name "Anonymous" would be used instead.

GET /hello HTTP/1.1
content-length: 0

Single Value

In addition to decoding to a Content struct, Vapor also supports fetching single values from the query string using subscripts.

let name: String? = req.query["name"]