Started to document Parameters.

README.md

@@ -29,7 +29,7 @@ let mediaType = MediaType(rawValue: rawMediaType)
 
 ### Suffixes and Parameters
 
-Media type ``Suffix``es and parameters are supported both via string literals and ``MediaType`` cases.
+Media type ``Suffix``es and ``Parameters`` are supported both via string literals and ``MediaType`` cases.
 
 ```swift
 MediaType.application(.atom(nil, ["charset": "utf-8"])) // is equivalent to

Sources/MediaType/Parameters.swift

@@ -1,5 +1,26 @@
 import Foundation
 
+/// Represents parameters of ``MediaType``s.
+///
+/// A media type may have parameters. For example `text/html;charset=utf-8` defines a media type with UTF-8 charset
+/// instead of the default ASCII.
+///
+/// You can specify arbitrary parameters to *any* of the ``MediaType``s using a Swift
+/// [dictionary](https://developer.apple.com/documentation/swift/dictionary). Keep in mind though, that not all such
+/// parameter values are registered (see the
+/// [official site](https://www.iana.org/assignments/media-types/media-types.xhtml) for details).
+///
+/// You can specify parameters by using either the Swift DSL or string literal syntax. Parameters in string variables
+/// are also supported. The following examples are equivalent:
+///
+/// ```swift
+/// let mediaType = MediaType.audio(.ac3(nil, ["rate": 32_000])) // is equivalent to
+///
+/// let mediaType: MediaType = "audio/ac3;rate=32000"  // is equivalent to
+///
+/// let rawMediaType = "audio/ac3;rate=32000"
+/// let mediaType = MediaType(rawValue: rawMediaType)
+/// ```
 public typealias Parameters = [String: CustomStringConvertible?]
 
 internal extension DefaultStringInterpolation {

Tests/MediaTypeTests/CodeExamples/CodeExamples+Parameters.swift

@@ -0,0 +1,15 @@
+import XCTest
+import MediaType
+
+extension CodeExamples {
+  func test_parameters_use_cases() {
+    let mediaType_A = MediaType.audio(.ac3(nil, ["rate": 32_000]))
+    let mediaType_B: MediaType = "audio/ac3;rate=32000"
+    let rawMediaType = "audio/ac3;rate=32000"
+    let mediaType_C = MediaType(rawValue: rawMediaType)
+
+    XCTAssertEqual(mediaType_A, mediaType_B)
+    XCTAssertEqual(mediaType_A, mediaType_C)
+    XCTAssertEqual(mediaType_B, mediaType_C)
+  }
+}