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Mixed choice/non-choice encoding (CoreOffice#154)
## Overview
Fixes bug encountered when encoding structs that hold a mixture of choice-element and non-choice-element (or multiple choice-element) properties.
## Example
Given a structure that stores both a choice and non-choice property,
```swift
private struct IntOrStringAndDouble: Equatable {
let intOrString: IntOrString
let decimal: Double
}
```
the natural encoding approach (now available) is
```swift
extension IntOrStringAndDouble: Encodable {
enum CodingKeys: String, CodingKey {
case decimal
}
func encode(to encoder: Encoder) {
try intOrString.encode(to: encoder)
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(decimal, forKey: .decimal)
}
}
```
The following `encode` implementation also works:
```swift
extension IntOrStringAndDouble: Encodable {
enum CodingKeys: String, CodingKey {
case decimal
}
func encode(to encoder: Encoder) {
var singleValueContainer = encoder.singleValueContainer()
try singleValueContainer.encode(intOrString)
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(decimal, forKey: .decimal)
}
}
```
`IntOrString` as defined in CoreOffice#119:
```swift
enum IntOrString: Equatable {
case int(Int)
case string(String)
}
extension IntOrString: Encodable {
enum CodingKeys: String, CodingKey {
case int
case string
}
func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
switch self {
case let .int(value):
try container.encode(value, forKey: .int)
case let .string(value):
try container.encode(value, forKey: .string)
}
}
}
extension IntOrString.CodingKeys: XMLChoiceCodingKey {} // signifies that `IntOrString` is a choice element
```
## Implementation Details
In cases where choice and non-choice elements (or multiple choice elements) co-exist in a keyed container, we merge them into a single `XMLKeyedEncodingContainer` (wrapping a `SharedBox<KeyedBox>`). Arrays of choice elements (using `XMLUnkeyedEncodingContainer` under the hood) are encoded the same way as before, as we do not hit the merging cases. For the array case, we still need the `XMLChoiceEncodingContainer` structure.
## Source Compatibility
This is an additive change.
* Add breaking case
* Add choice and keyed merging encode functionality
* Refactor
* Fix commented code
* Fix misnamed file
* Fix xcode project
* Fix precondition catch
* Use switch syntax
* Add multiple choice element case
* Add explicit types in KeyedBox initialization
* Add explicitly empty parameter to KeyedBox initializer
* Use more concise type inference
* Unify switch syntax
* Cut down code duplication
* Fix formatting- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,41 @@ | ||
| // | ||
| // IntOrString.swift | ||
| // XMLCoderTests | ||
| // | ||
| // Created by Benjamin Wetherfield on 11/24/19. | ||
| // | ||
|
|
||
| import XMLCoder | ||
|
|
||
| internal enum IntOrString: Equatable { | ||
| case int(Int) | ||
| case string(String) | ||
| } | ||
|
|
||
| extension IntOrString: Codable { | ||
| enum CodingKeys: String, CodingKey { | ||
| case int | ||
| case string | ||
| } | ||
|
|
||
| func encode(to encoder: Encoder) throws { | ||
| var container = encoder.container(keyedBy: CodingKeys.self) | ||
| switch self { | ||
| case let .int(value): | ||
| try container.encode(value, forKey: .int) | ||
| case let .string(value): | ||
| try container.encode(value, forKey: .string) | ||
| } | ||
| } | ||
|
|
||
| init(from decoder: Decoder) throws { | ||
| let container = try decoder.container(keyedBy: CodingKeys.self) | ||
| do { | ||
| self = .int(try container.decode(Int.self, forKey: .int)) | ||
| } catch { | ||
| self = .string(try container.decode(String.self, forKey: .string)) | ||
| } | ||
| } | ||
| } | ||
|
|
||
| extension IntOrString.CodingKeys: XMLChoiceCodingKey {} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,107 @@ | ||
| // | ||
| // MixedChoiceAndNonChoiceTests.swift | ||
| // XMLCoderTests | ||
| // | ||
| // Created by Benjamin Wetherfield on 11/24/19. | ||
| // | ||
|
|
||
| import XCTest | ||
| import XMLCoder | ||
|
|
||
| private struct MixedIntOrStringFirst: Equatable { | ||
| let intOrString: IntOrString | ||
| let otherValue: String | ||
| } | ||
|
|
||
| extension MixedIntOrStringFirst: Encodable { | ||
| enum CodingKeys: String, CodingKey { | ||
| case otherValue = "other-value" | ||
| } | ||
|
|
||
| func encode(to encoder: Encoder) throws { | ||
| try intOrString.encode(to: encoder) | ||
| var container = encoder.container(keyedBy: CodingKeys.self) | ||
| try container.encode(otherValue, forKey: .otherValue) | ||
| } | ||
| } | ||
|
|
||
| private struct MixedOtherFirst: Equatable { | ||
| let intOrString: IntOrString | ||
| let otherValue: String | ||
| } | ||
|
|
||
| extension MixedOtherFirst: Encodable { | ||
| enum CodingKeys: String, CodingKey { | ||
| case otherValue = "other-value" | ||
| } | ||
|
|
||
| func encode(to encoder: Encoder) throws { | ||
| var container = encoder.container(keyedBy: CodingKeys.self) | ||
| try container.encode(otherValue, forKey: .otherValue) | ||
| try intOrString.encode(to: encoder) | ||
| } | ||
| } | ||
|
|
||
| private struct MixedEitherSide { | ||
| let leading: String | ||
| let intOrString: IntOrString | ||
| let trailing: String | ||
| } | ||
|
|
||
| extension MixedEitherSide: Encodable { | ||
| enum CodingKeys: String, CodingKey { | ||
| case leading | ||
| case trailing | ||
| } | ||
|
|
||
| func encode(to encoder: Encoder) throws { | ||
| var container = encoder.container(keyedBy: CodingKeys.self) | ||
| try container.encode(leading, forKey: .leading) | ||
| try intOrString.encode(to: encoder) | ||
| try container.encode(trailing, forKey: .trailing) | ||
| } | ||
| } | ||
|
|
||
| private struct TwoChoiceElements { | ||
| let first: IntOrString | ||
| let second: IntOrString | ||
| } | ||
|
|
||
| extension TwoChoiceElements: Encodable { | ||
| func encode(to encoder: Encoder) throws { | ||
| try first.encode(to: encoder) | ||
| try second.encode(to: encoder) | ||
| } | ||
| } | ||
|
|
||
| class MixedChoiceAndNonChoiceTests: XCTestCase { | ||
| func testMixedChoiceFirstEncode() throws { | ||
| let first = MixedIntOrStringFirst(intOrString: .int(4), otherValue: "other") | ||
| let firstEncoded = try XMLEncoder().encode(first, withRootKey: "container") | ||
| let firstExpectedXML = "<container><int>4</int><other-value>other</other-value></container>" | ||
| XCTAssertEqual(String(data: firstEncoded, encoding: .utf8), firstExpectedXML) | ||
| } | ||
|
|
||
| func testMixedChoiceSecondEncode() throws { | ||
| let second = MixedOtherFirst(intOrString: .int(4), otherValue: "other") | ||
| let secondEncoded = try XMLEncoder().encode(second, withRootKey: "container") | ||
| let secondExpectedXML = "<container><other-value>other</other-value><int>4</int></container>" | ||
| XCTAssertEqual(String(data: secondEncoded, encoding: .utf8), secondExpectedXML) | ||
| } | ||
|
|
||
| func testMixedChoiceFlankedEncode() throws { | ||
| let flanked = MixedEitherSide(leading: "first", intOrString: .string("then"), trailing: "second") | ||
| let flankedEncoded = try XMLEncoder().encode(flanked, withRootKey: "container") | ||
| let flankedExpectedXML = """ | ||
| <container><leading>first</leading><string>then</string><trailing>second</trailing></container> | ||
| """ | ||
| XCTAssertEqual(String(data: flankedEncoded, encoding: .utf8), flankedExpectedXML) | ||
| } | ||
|
|
||
| func testTwoChoiceElementsEncode() throws { | ||
| let twoChoiceElements = TwoChoiceElements(first: .int(1), second: .string("one")) | ||
| let encoded = try XMLEncoder().encode(twoChoiceElements, withRootKey: "container") | ||
| let expectedXML = "<container><int>1</int><string>one</string></container>" | ||
| XCTAssertEqual(String(data: encoded, encoding: .utf8), expectedXML) | ||
| } | ||
| } |
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