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在 TypeScript 中,是否可以向枚举常量添加更多内容(属性、方法等),就像在 Java 中一样?
演示添加字段、方法和构造函数的 Java 示例:
public enum Planet {
MERCURY (3.303e+23, 2.4397e6),
VENUS (4.869e+24, 6.0518e6),
EARTH (5.976e+24, 6.37814e6),
MARS (6.421e+23, 3.3972e6),
JUPITER (1.9e+27, 7.1492e7),
SATURN (5.688e+26, 6.0268e7),
URANUS (8.686e+25, 2.5559e7),
NEPTUNE (1.024e+26, 2.4746e7);
private final double mass; // in kilograms
private final double radius; // in meters
Planet(double mass, double radius) {
this.mass = mass;
this.radius = radius;
}
private double mass() { return mass; }
private double radius() { return radius; }
// universal gravitational constant (m3 kg-1 s-2)
public static final double G = 6.67300E-11;
double surfaceGravity() {
return G * mass / (radius * radius);
}
double surfaceWeight(double otherMass) {
return otherMass * surfaceGravity();
}
// ...
}
最佳答案
不使用枚举,但您可以使用类和一些静态成员获得完全相同的东西:
class Planet {
public static MERCURY = new Planet(3.303e+23, 2.4397e6);
public static VENUS = new Planet(4.869e+24, 6.0518e6);
public static EARTH = new Planet(5.976e+24, 6.37814e6);
public static MARS = new Planet(6.421e+23, 3.3972e6);
public static JUPITER = new Planet(1.9e+27, 7.1492e7);
public static SATURN = new Planet(5.688e+26, 6.0268e7);
public static URANUS = new Planet(8.686e+25, 2.5559e7);
public static NEPTUNE = new Planet(1.024e+26, 2.4746e7);
private mass: number;
private radius: number;
private constructor(mass: number, radius: number) {
this.mass = mass;
this.radius = radius;
}
public static G = 6.67300E-11;
public surfaceGravity(): number {
return Planet.G * this.mass / (this.radius * this.radius);
}
public surfaceWeight(otherMass: number) {
return otherMass * this.surfaceGravity();
}
}
console.log(Planet.MERCURY.surfaceGravity());
在 java 中,为枚举中的每个项目创建一个静态实例,这意味着这确实做同样的事情,只是 java 有更好的语法来定义枚举。
这是一个具有等效 Planet.values()
的版本,java 将生成该版本:
class Planet {
public static MERCURY = new Planet(3.303e+23, 2.4397e6);
public static VENUS = new Planet(4.869e+24, 6.0518e6);
...
private static VALUES: Planet[] = [];
private mass: number;
private radius: number;
private constructor(mass: number, radius: number) {
this.mass = mass;
this.radius = radius;
Planet.VALUES.push(this);
}
public static values() {
return Planet.VALUES;
}
...
}
下面是实现 valueOf
的方法:
public static valueOf(name: string): Planet | null {
const names = Object.keys(this);
for (let i = 0; i < names.length; i++) {
if (this[names[i]] instanceof Planet && name.toLowerCase() === names[i].toLowerCase()) {
return this[names[i]];
}
}
return null;
}
关于java - TypeScript:向枚举添加更多数据,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/43376040/
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