Variables Vala-对象构造函数中的常量初始化和赋值
在过去的几天里,我一直在研究Vala编程语言,它看起来很有前途。但是,我不知道如何在对象构造中正确地分配常量(目前Vala相当于Variables Vala-对象构造函数中的常量初始化和赋值,variables,constructor,constants,vala,Variables,Constructor,Constants,Vala,在过去的几天里,我一直在研究Vala编程语言,它看起来很有前途。但是,我不知道如何在对象构造中正确地分配常量(目前Vala相当于final)。例如,在Java中: import java.lang.Math; public class Rectangle { public final double sideA; public final double sideB; public final double area; public final double dia
final
)。例如,在Java中:
import java.lang.Math;
public class Rectangle {
public final double sideA;
public final double sideB;
public final double area;
public final double diagonal;
public Rectangle (double SideA, double SideB) {
sideA = SideA;
sideB = SideB;
area = SideA * SideB;
diagonal = Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2));
}
}
这将如何用Vala编写?Vala没有Java的final关键字的直接等价物。我认为你能来的最近的地方是这样的:
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
public double area { get; construct; }
public double diagonal { get; construct; }
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
private double? _area = null;
public double area {
get {
if ( _area == null )
_area = sideA * sideB;
return _area;
}
}
private double? _diagonal = null;
public double diagonal {
get {
if ( _diagonal == null )
_diagonal = Math.sqrt(Math.pow(sideA, 2) + Math.pow(sideB, 2));
return _diagonal;
}
}
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
构造属性与final有点不同,这主要是因为GObject构造是如何工作的。它们只能在构造时设置,但与Java中的final不同(IIRC…我的大部分Java知识都被压抑了),它们也可以在构造期间由子类设置。例如,这是完全可以接受的:
public class Square : Rectangle {
public Square (double Side) {
GLib.Object (
sideA: Side,
sideB: Side,
area: Side * Side,
diagonal: Math.sqrt(Math.pow(Side, 2) + Math.pow(Side, 2)));
}
}
因此,如果您希望允许GObject样式的构造(如果您正在创建一个其他人将调用的库,我建议您这样做……如果代码只适合您,那么就没有必要),您可能需要执行以下操作:
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
public double area { get; construct; }
public double diagonal { get; construct; }
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
private double? _area = null;
public double area {
get {
if ( _area == null )
_area = sideA * sideB;
return _area;
}
}
private double? _diagonal = null;
public double diagonal {
get {
if ( _diagonal == null )
_diagonal = Math.sqrt(Math.pow(sideA, 2) + Math.pow(sideB, 2));
return _diagonal;
}
}
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
Vala没有Java的final关键字的直接等价物。我认为你能来的最近的地方是这样的:
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
public double area { get; construct; }
public double diagonal { get; construct; }
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
private double? _area = null;
public double area {
get {
if ( _area == null )
_area = sideA * sideB;
return _area;
}
}
private double? _diagonal = null;
public double diagonal {
get {
if ( _diagonal == null )
_diagonal = Math.sqrt(Math.pow(sideA, 2) + Math.pow(sideB, 2));
return _diagonal;
}
}
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
构造属性与final有点不同,这主要是因为GObject构造是如何工作的。它们只能在构造时设置,但与Java中的final不同(IIRC…我的大部分Java知识都被压抑了),它们也可以在构造期间由子类设置。例如,这是完全可以接受的:
public class Square : Rectangle {
public Square (double Side) {
GLib.Object (
sideA: Side,
sideB: Side,
area: Side * Side,
diagonal: Math.sqrt(Math.pow(Side, 2) + Math.pow(Side, 2)));
}
}
因此,如果您希望允许GObject样式的构造(如果您正在创建一个其他人将调用的库,我建议您这样做……如果代码只适合您,那么就没有必要),您可能需要执行以下操作:
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
public double area { get; construct; }
public double diagonal { get; construct; }
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
public class Rectangle : GLib.Object {
public double sideA { get; construct; }
public double sideB { get; construct; }
private double? _area = null;
public double area {
get {
if ( _area == null )
_area = sideA * sideB;
return _area;
}
}
private double? _diagonal = null;
public double diagonal {
get {
if ( _diagonal == null )
_diagonal = Math.sqrt(Math.pow(sideA, 2) + Math.pow(sideB, 2));
return _diagonal;
}
}
public Rectangle (double SideA, double SideB) {
GLib.Object (
sideA: SideA,
sideB: SideB,
area: SideA * SideB,
diagonal: Math.sqrt(Math.pow(SideA, 2) + Math.pow(SideB, 2)));
}
}
完美的这看起来比我目前的设置好多了。谢谢完美的这看起来比我目前的设置好多了。谢谢