Data_Class

Data Class

Intro

In Kotlin, a data class is a special type of class primarily designed to hold data. By using the data keyword, the compiler automatically generates several useful methods, reducing boilerplate code.

AI

Gemini

Requirements for a data class:

• The class declaration must start with the data keyword.
• It must have at least one parameter in the primary constructor.
• All primary constructor parameters must be declared as val or var.
• Data classes cannot be abstract, open, sealed, or inner.

Automatically generated methods:

• equals() and hashCode(): Determine object equality based on the properties in the primary constructor.
• toString(): Returns a string representation of the object in the format "ClassName(property1=value1, property2=value2, ...)".
• copy(): Creates a new object with the same properties as the original, but allows for selective property modification.
• componentN(): Functions that allow destructuring declarations, where N represents the position of the property in the primary constructor.

Limitations

• Data classes are designed for holding data and might not be suitable for complex logic or behavior.
• While data classes promote immutability by default using val, they don't enforce deep immutability for mutable properties.
• Data classes might not be ideal if inheritance or extensibility is a primary concern.

code

Define

data class User(val name: String, val age: Int)

public data class DeviceIdentityData(  
    public val xact: String,  
)

Access

fun main() {    
	val user1 = User("Alice", 30)    
	val user2 = User("Alice", 30)   
	val user3 = user1.copy(age = 31)    
	println(user1 == user2) // true, due to auto-generated equals()    
	println(user1) // User(name=Alice, age=30), due to auto-generated toString()    
	println(user3) // User(name=Alice, age=31), using the copy() method    
	val (name, age) = user1 // Destructuring declaration using componentN()    
	println("Name: $name, Age: $age") // Name: Alice, Age: 30
}