Codable is a type alias for the Encodable and Decodable protocols. According to Apple documentation “A type that can convert itself into and out of an external representation”.
Encodable Protocols:- The process in which custom type is converted into other representation is known as encoding or serialization. And to do so encodable protocols have to conform.
Decodable Protocols:- The process in which others’ representation is converted into your custom type is known as decoding or deserialization. And to do so decodable protocols have to conform.
And to support both encoding and decoding Codable protocols have to conform.
Let see an example.
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structEmployee:Codable{
varempId:Int?
varempname:String?
}
Now Employee type can be encoded and decoded both.
JSONEncoder
It is used to encode our type to another type. Like converting into data.
Let see an example.
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structEmployee:Codable{
varempId:Int?
varempname:String?
varemployeeDetails:EmployeeDetails?
}
structEmployeeDetails:Codable{
vardesignation:String?
varsalary:Double?
varage:Int?
varmobile:Int?
}
Now, we will encode Employee into data.
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let empDetails=EmployeeDetails(designation:"eng",salary:400000.00,age:25,mobile:512122121)
let employee=Employee(empId:101,empname:"test",employeeDetails:empDetails)
do{
let data=tryJSONEncoder().encode(employee)
print(data)
}catchleterr{
print(err.localizedDescription)
}
when we print the data it prints in Byte.
JSONDecoder
Now, we will convert the data again into Employee type.
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varempInData=Data()
let empDetails=EmployeeDetails(designation:"eng",salary:400000.00,age:25,mobile:512122121)
let employee=Employee(empId:101,empname:"test",employeeDetails:empDetails)
//Encoding
do{
let data=tryJSONEncoder().encode(employee)
empInData=data
print(data)
}catchleterr{
print(err.localizedDescription)
}
//Decoding
do{
let decodedData=tryJSONDecoder().decode(Employee.self,from:empInData)
If you only want to Encode then you have to conform to Encodable protocol and vice versa.
Coding Keys
If you want to use a different key name in your custom type than the actual JSON key. In that case, we will use CodingKeys enum. And will conforms CodingKey protocol.
Let see an example of it.
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structEmployeeDetails:Codable{
vardesignation:String?
varsalary:Double?
varage:Int?
varmobile:Int?
enumCodingKeys:String,CodingKey{
casedesignation
casesalary="emp_salary"
caseage="emp_age"
casemobile
}
}
Thanks for reading the Codable blog.
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