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参数属性 #118

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Feb 12, 2020
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参数属性 #118

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10 changes: 6 additions & 4 deletions advanced/class.md
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Original file line number Diff line number Diff line change
Expand Up @@ -280,20 +280,22 @@ let a = new Animal('Jack');
// index.ts(13,9): TS2674: Constructor of class 'Animal' is protected and only accessible within the class declaration.
```

修饰符还可以使用在构造函数参数中，等同于类中定义该属性，使代码更简洁。
### 参数属性

修饰符和`readonly`还可以使用在构造函数参数中，等同于类中定义该属性同时给该属性赋值，使代码更简洁。

```ts
class Animal {
// public name: string;
public constructor (public name) {
this.name = name;
// this.name = name;
}
}
```

### readonly

只读属性关键字，只允许出现在属性声明或索引签名中。
只读属性关键字，只允许出现在属性声明或索引签名或构造函数中。

```ts
class Animal {
Expand All @@ -316,7 +318,7 @@ a.name = 'Tom';
class Animal {
// public readonly name;
public constructor(public readonly name) {
this.name = name;
// this.name = name;
}
}
```
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