Swift — Codable

Wednesday, 18/03/2020

Tram Ho

I myself am not a fan of using the third library, usually in projects I always try to write in a pure library. If you are the same person, continue reading .

To be able to parse JSON in Swift until now I know that there are two libraries that many users are SwiftyJSON and ObjectMapper but if you do not like installing via Cocoapods or Carthage then use the apple provided, that is Codable

Codable is an alias of two protocols: Decodable & Encodable , Codable protocol is used to convert JSON data object into a class or struct in Swift, this process is called Decoding because JSON data is decoded into a format that Swift understands. Codable can also encode (encoding) Swift objects into JSON.

Swift Codable basic

We will go into the first example of Swift Codable, the goal will be to convert the following JSON into Swift object (struct)

<span class="token keyword">let</span> jsonString <span class="token operator">=</span> <span class="token string">""</span> "
<span class="token punctuation">{</span>
    <span class="token string">"first_name"</span> <span class="token punctuation">:</span> <span class="token string">"Ngo"</span> <span class="token punctuation">,</span>
    <span class="token string">"last_name"</span> <span class="token punctuation">:</span> <span class="token string">"Viet Anh"</span> <span class="token punctuation">,</span>
    <span class="token string">"country"</span> <span class="token punctuation">:</span> <span class="token string">"Viet Nam"</span> <span class="token punctuation">,</span>
    <span class="token string">"age"</span> <span class="token punctuation">:</span> <span class="token number">20</span>
<span class="token punctuation">}</span>
<span class="token string">""</span> "

let jsonString = "" "

{

"first_name" : "Ngo" ,

"last_name" : "Viet Anh" ,

"country" : "Viet Nam" ,

"age" : 20

}

"" "

Making:

For simple JSON forms like this, just create a struct conform Codable protocol for accuracy, then use JSONDecoder () to decode the instance. Note: If no encode is needed, just conforming to the Decodable protocol is sufficient.

<span class="token keyword">struct</span> <span class="token builtin">Person</span> <span class="token punctuation">:</span> <span class="token builtin">Codable</span> <span class="token punctuation">{</span>
    <span class="token keyword">var</span> first_name <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
    <span class="token keyword">var</span> last_name <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
    <span class="token keyword">var</span> country <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
    <span class="token keyword">var</span> age <span class="token punctuation">:</span> <span class="token builtin">Int</span> <span class="token operator">=</span> <span class="token number">0</span>
<span class="token punctuation">}</span>

<span class="token comment">// Convert json string to data</span>
<span class="token keyword">var</span> data <span class="token operator">=</span> <span class="token function">Data</span> <span class="token punctuation">(</span> jsonString <span class="token punctuation">.</span> utf8 <span class="token punctuation">)</span>
<span class="token keyword">let</span> decoder <span class="token operator">=</span> <span class="token function">JSONDecoder</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span>
<span class="token comment">// Decode json with dictionary</span>
<span class="token keyword">let</span> personEntity <span class="token operator">=</span> <span class="token keyword">try</span> <span class="token operator">?</span> decoder <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token builtin">Person</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> from <span class="token punctuation">:</span> data <span class="token punctuation">)</span>
<span class="token keyword">if</span> <span class="token keyword">let</span> personEntity <span class="token operator">=</span> personEntity <span class="token punctuation">{</span>
    <span class="token function">print</span> <span class="token punctuation">(</span> personEntity <span class="token punctuation">)</span>
    <span class="token comment">/// Person(first_name: "Ngo", last_name: "Viet Anh", country: "Viet Nam", age: 20)</span>
<span class="token punctuation">}</span>

struct Person : Codable {

var first_name : String = ""

var last_name : String = ""

var country : String = ""

var age : Int = 0

}

// Convert json string to data

var data = Data ( jsonString . utf8 )

let decoder = JSONDecoder ( )

// Decode json with dictionary

let personEntity = try ? decoder . decode ( Person . self , from : data )

if let personEntity = personEntity {

print ( personEntity )

/// Person(first_name: "Ngo", last_name: "Viet Anh", country: "Viet Nam", age: 20)

}

For array form like this

[{
    "first_name": "Ngo",
    "last_name": "Viet Anh",
    "country": "Viet Nam",
    "age": 20
},
{
    "first_name": "Dang",
    "last_name": "Thanh Dat",
    "country": "Viet Nam",
    "age": 69
}]

[{

"first_name": "Ngo",

"last_name": "Viet Anh",

"country": "Viet Nam",

"age": 20

{

"first_name": "Dang",

"last_name": "Thanh Dat",

"country": "Viet Nam",

"age": 69

}]

Then just add the array where the decode is

<span class="token keyword">let</span> personEntity <span class="token operator">=</span> <span class="token keyword">try</span> <span class="token operator">?</span> decoder <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token punctuation">[</span> <span class="token builtin">Person</span> <span class="token punctuation">]</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> from <span class="token punctuation">:</span> data <span class="token punctuation">)</span>

let personEntity = try ? decoder . decode ( [ Person ] . self , from : data )

Swift Codable manual encode decode

For json like this

<span class="token keyword">let</span> jsonString <span class="token operator">=</span> <span class="token string">""</span> "
<span class="token punctuation">{</span>
    <span class="token string">"person_detail"</span> <span class="token punctuation">:</span> <span class="token punctuation">{</span>
        <span class="token string">"first_name"</span> <span class="token punctuation">:</span> <span class="token string">"Ngo"</span> <span class="token punctuation">,</span>
        <span class="token string">"last_name"</span> <span class="token punctuation">:</span> <span class="token string">"Viet Anh"</span> <span class="token punctuation">,</span>
        <span class="token string">"country"</span> <span class="token punctuation">:</span> <span class="token string">"Viet Nam"</span> <span class="token punctuation">,</span>
        <span class="token string">"age"</span> <span class="token punctuation">:</span> <span class="token number">20</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
<span class="token string">""</span> "

let jsonString = "" "

{

"person_detail" : {

"first_name" : "Ngo" ,

"last_name" : "Viet Anh" ,

"country" : "Viet Nam" ,

"age" : 20

}

"" "

To handle then we do the following

<span class="token keyword">struct</span> <span class="token builtin">PersonData</span> <span class="token punctuation">:</span> <span class="token builtin">Codable</span> <span class="token punctuation">{</span>
    
    <span class="token keyword">struct</span> <span class="token builtin">Person</span> <span class="token punctuation">:</span> <span class="token builtin">Codable</span> <span class="token punctuation">{</span>
        <span class="token keyword">var</span> first_name <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
        <span class="token keyword">var</span> last_name <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
        <span class="token keyword">var</span> country <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
        <span class="token keyword">var</span> age <span class="token punctuation">:</span> <span class="token builtin">Int</span> <span class="token operator">=</span> <span class="token number">0</span>
    <span class="token punctuation">}</span>
    
    <span class="token keyword">var</span> person_detail <span class="token punctuation">:</span> <span class="token builtin">Person</span>
<span class="token punctuation">}</span>

<span class="token keyword">var</span> data <span class="token operator">=</span> <span class="token function">Data</span> <span class="token punctuation">(</span> jsonString <span class="token punctuation">.</span> utf8 <span class="token punctuation">)</span>
<span class="token keyword">let</span> decoder <span class="token operator">=</span> <span class="token function">JSONDecoder</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span>
<span class="token comment">// Decode json with dictionary</span>
<span class="token keyword">let</span> personEntity <span class="token operator">=</span> <span class="token keyword">try</span> <span class="token operator">?</span> decoder <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token builtin">PersonData</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> from <span class="token punctuation">:</span> data <span class="token punctuation">)</span>
<span class="token keyword">if</span> <span class="token keyword">let</span> personEntity <span class="token operator">=</span> personEntity <span class="token punctuation">{</span>
    <span class="token function">print</span> <span class="token punctuation">(</span> personEntity <span class="token punctuation">.</span> person_detail <span class="token punctuation">)</span>
<span class="token punctuation">}</span>

struct PersonData : Codable {

var age : Int = 0

}

var person_detail : Person

}

// Decode json with dictionary

let personEntity = try ? decoder . decode ( PersonData . self , from : data )

if let personEntity = personEntity {

print ( personEntity . person_detail )

}

Swift Codable coding key

In most cases, the client will use the json format that the server has already defined, so json types of the above format may be encountered, but if Struct can be codable, the need to define properties as person_detail, first_name. This violates the coding convention of Swift. In this case we use the Coding key to map between the properties of Struct and the key of JSON.

<span class="token keyword">struct</span> <span class="token builtin">Person</span> <span class="token punctuation">{</span>
    
    <span class="token keyword">var</span> firstName <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
    <span class="token keyword">var</span> lastName <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
    <span class="token keyword">var</span> country <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token operator">=</span> <span class="token string">""</span>
    <span class="token keyword">var</span> age <span class="token punctuation">:</span> <span class="token builtin">Int</span> <span class="token operator">=</span> <span class="token number">0</span>
    
    <span class="token keyword">enum</span> <span class="token builtin">PersonKeys</span> <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token punctuation">,</span> <span class="token builtin">CodingKey</span> <span class="token punctuation">{</span>
        <span class="token keyword">case</span> person <span class="token operator">=</span> <span class="token string">"person_detail"</span>
    <span class="token punctuation">}</span>
    <span class="token keyword">enum</span> <span class="token builtin">PersonDetailKeys</span> <span class="token punctuation">:</span> <span class="token builtin">String</span> <span class="token punctuation">,</span> <span class="token builtin">CodingKey</span> <span class="token punctuation">{</span>
        <span class="token keyword">case</span> firstName <span class="token operator">=</span> <span class="token string">"first_name"</span>
        <span class="token keyword">case</span> lastName <span class="token operator">=</span> <span class="token string">"last_name"</span>
        <span class="token keyword">case</span> country
        <span class="token keyword">case</span> age
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

struct Person {

var firstName : String = ""

var lastName : String = ""

var age : Int = 0

enum PersonKeys : String , CodingKey {

case person = "person_detail"

}

enum PersonDetailKeys : String , CodingKey {

case firstName = "first_name"

case lastName = "last_name"

case country

case age

}

To decode


<span class="token keyword">extension</span> <span class="token builtin">Person</span> <span class="token punctuation">:</span> <span class="token builtin">Decodable</span> <span class="token punctuation">{</span>
    <span class="token keyword">init</span> <span class="token punctuation">(</span> from decoder <span class="token punctuation">:</span> <span class="token builtin">Decoder</span> <span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token punctuation">{</span>
        <span class="token keyword">let</span> personContainer <span class="token operator">=</span> <span class="token keyword">try</span> decoder <span class="token punctuation">.</span> <span class="token function">container</span> <span class="token punctuation">(</span> keyedBy <span class="token punctuation">:</span> <span class="token builtin">PersonKeys</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">)</span>
        
        <span class="token keyword">let</span> personDetailContainer <span class="token operator">=</span> <span class="token keyword">try</span> personContainer <span class="token punctuation">.</span> <span class="token function">nestedContainer</span> <span class="token punctuation">(</span> keyedBy <span class="token punctuation">:</span> <span class="token builtin">PersonDetailKeys</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> person <span class="token punctuation">)</span>
        firstName <span class="token operator">=</span> <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token builtin">String</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> firstName <span class="token punctuation">)</span>
        lastName <span class="token operator">=</span> <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token builtin">String</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> lastName <span class="token punctuation">)</span>
        country <span class="token operator">=</span> <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token builtin">String</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> country <span class="token punctuation">)</span>
        age <span class="token operator">=</span> <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">decode</span> <span class="token punctuation">(</span> <span class="token builtin">Int</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> age <span class="token punctuation">)</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

extension Person : Decodable {

init ( from decoder : Decoder ) throws {

let personContainer = try decoder . container ( keyedBy : PersonKeys . self )

let personDetailContainer = try personContainer . nestedContainer ( keyedBy : PersonDetailKeys . self , forKey : . person )

firstName = try personDetailContainer . decode ( String . self , forKey : . firstName )

lastName = try personDetailContainer . decode ( String . self , forKey : . lastName )

country = try personDetailContainer . decode ( String . self , forKey : . country )

age = try personDetailContainer . decode ( Int . self , forKey : . age )

}

In case it is necessary to encode to send to the server then

<span class="token keyword">extension</span> <span class="token builtin">Person</span> <span class="token punctuation">:</span> <span class="token builtin">Encodable</span> <span class="token punctuation">{</span>
    <span class="token keyword">func</span> <span class="token function">encode</span> <span class="token punctuation">(</span> to encoder <span class="token punctuation">:</span> <span class="token builtin">Encoder</span> <span class="token punctuation">)</span> <span class="token keyword">throws</span> <span class="token punctuation">{</span>
        <span class="token keyword">var</span> personContainer <span class="token operator">=</span> encoder <span class="token punctuation">.</span> <span class="token function">container</span> <span class="token punctuation">(</span> keyedBy <span class="token punctuation">:</span> <span class="token builtin">PersonKeys</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">)</span>
        <span class="token keyword">var</span> personDetailContainer <span class="token operator">=</span> personContainer <span class="token punctuation">.</span> <span class="token function">nestedContainer</span> <span class="token punctuation">(</span> keyedBy <span class="token punctuation">:</span> <span class="token builtin">PersonDetailKeys</span> <span class="token punctuation">.</span> <span class="token keyword">self</span> <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> person <span class="token punctuation">)</span>

        <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">encode</span> <span class="token punctuation">(</span> firstName <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> firstName <span class="token punctuation">)</span>
        <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">encode</span> <span class="token punctuation">(</span> lastName <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> lastName <span class="token punctuation">)</span>
        <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">encode</span> <span class="token punctuation">(</span> country <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> country <span class="token punctuation">)</span>
        <span class="token keyword">try</span> personDetailContainer <span class="token punctuation">.</span> <span class="token function">encodeIfPresent</span> <span class="token punctuation">(</span> age <span class="token punctuation">,</span> forKey <span class="token punctuation">:</span> <span class="token punctuation">.</span> age <span class="token punctuation">)</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

<span class="token keyword">let</span> encoder <span class="token operator">=</span> <span class="token function">JSONEncoder</span> <span class="token punctuation">(</span> <span class="token punctuation">)</span>
<span class="token comment">// Encode instance to Data</span>
<span class="token keyword">if</span> <span class="token keyword">let</span> personEntity <span class="token operator">=</span> personEntity <span class="token punctuation">{</span>
    <span class="token keyword">let</span> personData <span class="token operator">=</span> <span class="token keyword">try</span> <span class="token operator">?</span> encoder <span class="token punctuation">.</span> <span class="token function">encode</span> <span class="token punctuation">(</span> personEntity <span class="token punctuation">)</span>
    <span class="token keyword">if</span> <span class="token keyword">let</span> personData <span class="token operator">=</span> personData <span class="token punctuation">{</span>
        <span class="token function">print</span> <span class="token punctuation">(</span> personData <span class="token punctuation">)</span>
        <span class="token comment">///91 bytes</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>

extension Person : Encodable {

func encode ( to encoder : Encoder ) throws {

var personContainer = encoder . container ( keyedBy : PersonKeys . self )

var personDetailContainer = personContainer . nestedContainer ( keyedBy : PersonDetailKeys . self , forKey : . person )

try personDetailContainer . encode ( firstName , forKey : . firstName )

try personDetailContainer . encode ( lastName , forKey : . lastName )

try personDetailContainer . encode ( country , forKey : . country )

try personDetailContainer . encodeIfPresent ( age , forKey : . age )

}

let encoder = JSONEncoder ( )

// Encode instance to Data

if let personEntity = personEntity {

let personData = try ? encoder . encode ( personEntity )

if let personData = personData {

print ( personData )

///91 bytes

}

It's a bit long, but building yourself in this way is dangerous too

With the above hope you will understand and feel comfortable using Codable. The first article has many shortcomings, hope everyone helps.

Source: https://nhathm.com/swift-codable-1-24d7d95584f1

Share the news now

Source : Viblo

Swift — Codable

Swift Codable basic

Making:

For array form like this

Swift Codable manual encode decode

Swift Codable coding key

To decode

In case it is necessary to encode to send to the server then

TikTok becomes the second largest social platform in South Africa

The fastest depreciating after 9 months of launch, iPhone 14 Pro Max continues to break the bottom in Vietnam

Beginner's guide to R: Introduction

10 essential SublimeText plugins for JavaScript developers