Creating struct Instances
After defining a struct type, you can create struct instances by calling the struct's constructor. Outside the struct definition, you create an instance of the type by calling the constructor with the struct type name, and you can access instance member variables and instance member functions that satisfy visibility modifiers (such as public) through the instance. For example, in the following code, a variable r of type Rectangle is defined. You can access the values of width and height in r through r.width and r.height, respectively, and call the member function area of r through r.area().
If you want to modify the values of member variables through a struct instance, you need to define the struct variable as mutable, and the member variable being modified must also be mutable (defined with var). Here's an example:
During assignment or parameter passing, a struct instance is copied (for reference-type member variables, only the reference is copied, not the referenced object), generating a new instance. Modifying one instance does not affect the other. For example, in the following code, after assigning r1 to r2, modifying the width and height values of r1 does not affect the width and height values of r2.
struct Rectangle {
public var width: Int64
public var height: Int64
public init(width: Int64, height: Int64) {
this.width = width
this.height = height
}
public func area() {
width * height
}
}
let r = Rectangle(10, 20)
let width = r.width // width = 10
let height = r.height // height = 20
let a = r.area() // a = 200struct Rectangle {
public var width: Int64
public var height: Int64
public init(width: Int64, height: Int64) {
this.width = width
this.height = height
}
public func area() {
width * height
}
}
main() {
var r = Rectangle(10, 20) // r.width = 10, r.height = 20
r.width = 8 // r.width = 8
r.height = 24 // r.height = 24
let a = r.area() // a = 192
}struct Rectangle {
public var width: Int64
public var height: Int64
public init(width: Int64, height: Int64) {
this.width = width
this.height = height
}
public func area() {
width * height
}
}
main() {
var r1 = Rectangle(10, 20) // r1.width = 10, r1.height = 20
var r2 = r1 // r2.width = 10, r2.height = 20
r1.width = 8 // r1.width = 8
r1.height = 24 // r1.height = 24
let a1 = r1.area() // a1 = 192
let a2 = r2.area() // a2 = 200
}