[英]In Typescript, what is the difference between type and interface?
What are the differences between the following?以下有什么区别?
type Foo = {
foo: string
};
interface Foo {
foo: string;
}
Interfaces can be extended接口可以扩展
interface A {
x: number;
}
interface B extends A {
y: string;
}
and also augmented并且还增加了
interface C {
m: boolean;
}
// ... later ...
interface C {
n: number;
}
Type aliases, however, can represent some things interfaces can't然而,类型别名可以代表一些接口不能代表的东西
type NumOrStr = number | string;
type NeatAndCool = Neat & Cool;
type JustSomeOtherName = SomeType;
So in general if you just have a plain object type, as shown in your question, an interface is usually a better approach.所以一般来说,如果你只有一个普通的对象类型,如你的问题所示,接口通常是更好的方法。 If you find yourself wanting to write something that can't be written as an interface, or want to just give something a different name, a type alias is better.
如果你发现自己想写一些不能写成接口的东西,或者只想给一些东西一个不同的名字,类型别名更好。
Differences between these too are already in this thread.这些之间的差异也已经在这个线程中。
type Foo = {
foo: string
};
interface Foo {
foo: string;
}
Here type Foo
and interface Foo
looks almost similar so its confusing.这里的
type Foo
和interface Foo
看起来几乎相似,所以很容易混淆。
interface
is contract that the following properties (here foo:string
) should be there in a object. interface
约定以下属性(此处为foo:string
)应存在于对象中。 interface
is not class
. interface
不是class
。 It is used when language does not support Multiple Inheritance.当语言不支持多重继承时使用它。 So
interface
can be a common structure between different classes.所以
interface
可以是不同类之间的公共结构。
class Bar implements Foo {
foo: string;
}
let p: Foo = { foo: 'a string' };
But type
and interface
are used in very different context.但是
type
和interface
在非常不同的上下文中使用。
let foo: Foo;
let today: Date = new Date();
Here type
of foo
is Foo
and today
is Date
.这里的
foo
type
是Foo
, today
是Date
。 Its like a variable decleration which holds the information of typeof other variable.它就像一个变量声明,它保存了其他变量的类型信息。
type
is like a superset of interfaces, classes, function signature, other types or even values (like type mood = 'Good' | 'Bad'
). type
就像接口、类、函数签名、其他类型甚至值的超集(例如type mood = 'Good' | 'Bad'
)。 At the end type
describes the possible structure or value of a variable.最后,
type
描述了变量的可能结构或值。
It is wrong to say "Interfaces can be implemented" since types can also be implemented说“接口可以实现”是错误的,因为类型也可以实现
type A = { a: string };
class Test implements A {
a: string;
}
Although you can do this, you can't implement a type that is a Union of types, which makes totally sense honestly :)虽然你可以做到这一点,但你不能实现一个类型的联合,老实说这是完全合理的:)
Types is kinda like Interfaces and vice versa: both can implemented by a class.类型有点像接口,反之亦然:两者都可以由类实现。 but there are some important differences: 1. when Type is implemented by a class, the properties which belong to the Type must be initialized inside the class, whereas with Interface they must be declared.
但是有一些重要的区别: 1. 当Type由类实现时,属于Type的属性必须在类内部初始化,而对于Interface,它们必须声明。 2. as @ryan mentioned : Interface can extend another Interface.
2. 正如@ryan 提到的:接口可以扩展另一个接口。 Types cannot.
类型不能。
type Person = {
name:string;
age:number;
}
// must initialize all props - unlike interface
class Manager implements Person {
name: string = 'John';
age: number = 55;
// can add props and methods
size:string = 'm';
}
const jane : Person = {
name :'Jane',
age:46,
// cannot add more proprs or methods
//size:'s'
}
type in the typescript is used to reference already existing types . type 在打字稿中用于引用已经存在的类型。 It can not be extended like
interface
.它不能像
interface
那样扩展。 Examples of type
are: type
例子是:
type Money = number;
type FormElem = React.FormEvent<HTMLFormElement>;
type Person = [string, number, number];
you can use Rest and Spread in types:您可以在以下类型中使用 Rest 和 Spread:
type Scores = [string, ...number[]];
let ganeshScore = ["Ganesh", 10, 20, 30]
let binodScore = ["Binod", 10, 20, 30, 40]
Interface, on the other hand, allows you to create a NEW TYPE.另一方面,界面允许您创建新类型。
interface Person{
name: string,
age: number,
}
Interface can be extended with extends keyword.
interface Todo{
text: string;
complete: boolean;
}
type Tags = [string, string, string]
interface TaggedTodo extends Todo{
tags: Tags
}
此外,还可以实现接口。
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