Question

我试图在我在Typescript中定义的NodeJ中创建和使用一些数据类，而这正是我想知道是否有更简单的方法。

在javascript中我能够做到

let myBuilding = new Building

那我就可以做

myBuilding.col1 = "Wall"
myBuilding.col2 = "None"

以此类推

在打字稿中，如果我没有在声明时声明所有内容，它就不会喜欢它。有没有办法用空值初始化一个类，然后再分配它们呢？当某些东西没有赋值时，也会发生什么呢？在javascript中，我们没有得到返回的项目，这在从json解析为类时非常有用

这是我的一类人

export class Exterior {
    public exterior: string;
    public fencing: string;
    public security: string;
    public sewer: string;
    public lot: string;
    public pool: string;
    public patioPorch: string;
    public spa: string;

    constructor(exterior: string, fencing: string, security: string, sewer: string, lot: string, pool: string,
                patioPorch: string, spa: string) {

        this.exterior = exterior;
        this.fencing = fencing;
        this.security = security;
        this.sewer = sewer;
        this.lot = lot;
        this.pool = pool;
        this.patioPorch = patioPorch;
        this.spa = spa;
    }
}

Answer 1

以下是实现此目的的四种方法：

class Foo {
    // This will not do anything, so remove it
    constructor() {}

    // this will be undefined initially
    private internalA!: number;

    public get fieldA() {
        return this.internalA
    }

    public set fieldA(internalAValue: number) {
        this.internalA = internalAValue;
    }

    // this will be undefined initially
    public fieldB!: boolean;
    // this will be undefined initially
    public fieldC!: string;
    // this will be "example-initial-value" initially
    public fieldD: string = "example-initial-value";
}

const foo = new Foo();

// Method 1 using setters
foo.fieldA = 2;
alert(foo.fieldA);

// Method 2 using simple assigning
foo.fieldB = true;
alert(foo.fieldB);

// Method 3 using Object.defineProperty
Object.defineProperty(foo, 'fieldC', {
  value: "test",
  writable: false
});
alert(foo.fieldC);

// Method 4 using Object.assign
Object.assign(foo, {fieldD: "hello"});
alert(foo.fieldD);

非常小心，甚至直接避免使用Object.defineProperty和Object.assign，而无需创建用于强制类型的包装器。他们都有很多避开/忘记类型系统的方法。

设置方法和直接公共领域分配是最简单的类型安全方式。

You can run it here

这是一种无需先初始化即可一次性设置多项功能的方法

interface IFooParams {
    fieldA: number;
    fieldB: boolean;
    fieldC: string;
    fieldD: string
}

class Foo {
    // this will be undefined initially
    public fieldA!: number;
    // this will be undefined initially
    public fieldB!: boolean;
    // this will be undefined initially
    public fieldC!: string;
    // this will be "example-initial-value" initially
    public fieldD: string = "example-initial-value";

    public setAllInOneGo(params: IFooParams): void {
        this.fieldA = params.fieldA;
        this.fieldB = params.fieldB;
        this.fieldC = params.fieldC;
        this.fieldD = params.fieldD;
    }
}

const foo = new Foo();

// Whenever:
foo.setAllInOneGo({
    fieldA: 2,
    fieldB: false,
    fieldC: "hello",
    fieldD: "world"
});

Answer 2

当您声明类型时，您可以将其设置为可选：

class Building {
  height?: number;
}

如果您不立即声明高度，但是现在打字稿将不会抱怨，但是您仍然无法添加额外的未声明字段，例如宽度。

如果它们满足接口的某些子集，但不是所有必填字段，则也可以将其声明为Partial<Building>。

NodeJS中的Typescript类

2 个答案: