XMLCoder

Encoder & Decoder for XML using Swift's Codable protocols.

This package is a fork of the original ShawnMoore/XMLParsing with more features and improved test coverage.

Example

import XMLCoder

let xmlStr = """
<note>
    <to>Bob</to>
    <from>Jane</from>
    <heading>Reminder</heading>
    <body>Don't forget to use XMLCoder!</body>
</note>
"""

struct Note: Codable {
    let to: String
    let from: String
    let heading: String
    let body: String
}

guard let data = xmlStr.data(using: .utf8) else { return }

let note = try? XMLDecoder().decode(Note.self, from: data)

let returnData = try? XMLEncoder().encode(note, withRootKey: "note")

Advanced features

These features are available in 0.4.0 release or later:

Stripping namespace prefix

Sometimes you need to handle an XML namespace prefix, like in the XML below:

<h:table xmlns:h="http://www.w3.org/TR/html4/">
  <h:tr>
    <h:td>Apples</h:td>
    <h:td>Bananas</h:td>
  </h:tr>
</h:table>

Stripping the prefix from element names is enabled with shouldProcessNamespaces property:

struct Table: Codable, Equatable {
    struct TR: Codable, Equatable {
        let td: [String]
    }

    let tr: [TR]
}


let decoder = XMLDecoder()

// Setting this property to `true` for the namespace prefix to be stripped
// during decoding so that key names could match.
decoder.shouldProcessNamespaces = true

let decoded = try decoder.decode(Table.self, from: xmlData)

Dynamic node coding

XMLCoder provides two helper protocols that allow you to customize whether nodes are encoded and decoded as attributes or elements: DynamicNodeEncoding and DynamicNodeDecoding.

The declarations of the protocols are very simple:

protocol DynamicNodeEncoding: Encodable {
    static func nodeEncoding(for key: CodingKey) -> XMLEncoder.NodeEncoding
}

protocol DynamicNodeDecoding: Decodable {
    static func nodeDecoding(for key: CodingKey) -> XMLDecoder.NodeDecoding
}

The values returned by corresponding static functions look like this:

enum NodeDecoding {
    // decodes a value from an attribute
    case attribute

    // decodes a value from an element
    case element

    // the default, attempts to decode as an element first,
    // otherwise reads from an attribute
    case elementOrAttribute 
}

enum NodeEncoding {
    // encodes a value in an attribute
    case attribute

    // the default, encodes a value in an element
    case element

    // encodes a value in both attribute and element
    case both
}

Add conformance to an appropriate protocol for types you'd like to customize. Accordingly, this example code:

struct Book: Codable, Equatable, DynamicNodeEncoding {
    let id: UInt
    let title: String
    let categories: [Category]

    enum CodingKeys: String, CodingKey {
        case id
        case title
        case categories = "category"
    }

    static func nodeEncoding(forKey key: CodingKey) 
    -> XMLEncoder.NodeEncoding {
        switch key {
        case Book.CodingKeys.id: return .both
        default: return .element
        }
    }
}

works for this XML:

<book id="123">
    <id>123</id>
    <title>Cat in the Hat</title>
    <category>Kids</category>
    <category>Wildlife</category>
</book>

Coding key value intrinsic

Suppose that you need to decode an XML that looks similar to this:

<?xml version="1.0" encoding="UTF-8"?>
<foo id="123">456</foo>

By default you'd be able to decode foo as an element, but then it's not possible to decode the id attribute. XMLCoder handles certain CodingKey values in a special way to allow proper coding for this XML. Just add a coding key with stringValue that equals "value" or "" (empty string). What follows is an example type declaration that encodes the XML above, but special handling of coding keys with those values works for both encoding and decoding.

struct Foo: Codable, DynamicNodeEncoding {
    let id: String
    let value: String

    enum CodingKeys: String, CodingKey {
        case id
        case value
        // case value = "" would also work
    }

    static func nodeEncoding(forKey key: CodingKey) 
    -> XMLEncoder.NodeEncoding {
        switch key {
        case CodingKeys.id:
            return .attribute
        default:
            return .element
        }
    }
}

Preserving whitespaces in element content

By default whitespaces are trimmed in element content during decoding. This includes string values decoded with value intrinsic keys. Starting with version 0.5 you can now set a property trimValueWhitespaces to false (the default value is true) on XMLDecoder instance to preserve all whitespaces in decoded strings.

Installation

Requirements

Xcode 10.0 or later
Swift 4.2 or later
iOS 9.0 / watchOS 2.0 / tvOS 9.0 / macOS 10.10 or later

CocoaPods

CocoaPods is a dependency manager for Swift and Objective-C Cocoa projects. You can install it with the following command:

$ gem install cocoapods

Navigate to the project directory and create Podfile with the following command:

$ pod install

Inside of your Podfile, specify the XMLCoder pod:

# Uncomment the next line to define a global platform for your project
# platform :ios, '9.0'

target 'YourApp' do
  # Comment the next line if you're not using Swift and don't want to use dynamic frameworks
  use_frameworks!

  # Pods for Test
  pod 'XMLCoder', '~> 0.5.1'

end

Then, run the following command:

$ pod install

Open the the YourApp.xcworkspace file that was created. This should be the file you use everyday to create your app, instead of the YourApp.xcodeproj file.

Carthage

Carthage is a dependency manager that builds your dependencies and provides you with binary frameworks.

Carthage can be installed with Homebrew using the following command:

$ brew update
$ brew install carthage

Inside of your Cartfile, add GitHub path to XMLCoder:

github "MaxDesiatov/XMLCoder" ~> 0.5.1

Then, run the following command to build the framework:

$ carthage update

Drag the built framework into your Xcode project.

Swift Package Manager

Swift Package Manager is a tool for managing the distribution of Swift code. It’s integrated with the Swift build system to automate the process of downloading, compiling, and linking dependencies.

Once you have your Swift package set up, adding XMLCoder as a dependency is as easy as adding it to the dependencies value of your Package.swift.

dependencies: [
    .package(url: "https://github.com/MaxDesiatov/XMLCoder.git", from: "0.5.1")
]

Contributing

This project adheres to the Contributor Covenant Code of Conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to xmlcoder@desiatov.com.

Coding Style

This project uses SwiftFormat to enforce formatting style. We encourage you to run SwiftFormat within a local clone of the repository in whatever way works best for you either manually or automatically via an Xcode extension, build phase or git pre-commit hook etc. Please check SwiftFormat documentation for more details.

SwiftFormat also runs within our Travis CI setup and a CI build can fail with incosistent formatting. We require CI builds to pass for any PR before merging.

Test Coverage

Our goal is to keep XMLCoder stable and to serialize any XML correctly according to XML 1.0 standard. All of this can be easily tested automatically and we're slowly improving test coverage of XMLCoder and don't expect it to decrease. PRs that decrease the test coverage have a much lower chance of being merged. If you add any new features, please make sure to add tests, likewise for changes and any refactoring in existing code.

grin/XMLCoder