class-methods-use-this
强制类方法使用 this
如果一个类方法不使用 this，有时可以做成静态函数。如果你确实将该方法转换为静态函数，则调用该特定方法的类的实例也必须转换为静态调用（MyClass.callStaticMethod()）
¥If a class method does not use this, it can sometimes be made into a static function. If you do convert the method into a static function, instances of the class that call that particular method have to be converted to a static call as well (MyClass.callStaticMethod())
可能有一个不使用 this 的类方法，例如：
¥It’s possible to have a class method which doesn’t use this, such as:
class A {
constructor() {
this.a = "hi";
}
print() {
console.log(this.a);
}
sayHi() {
console.log("hi");
}
}
let a = new A();
a.sayHi(); // => "hi"
在上面的例子中，sayHi 方法没有使用 this，所以我们可以把它变成一个静态方法：
¥In the example above, the sayHi method doesn’t use this, so we can make it a static method:
class A {
constructor() {
this.a = "hi";
}
print() {
console.log(this.a);
}
static sayHi() {
console.log("hi");
}
}
A.sayHi(); // => "hi"
还要注意，在上面的示例中，如果将方法切换为静态方法，则必须将调用静态方法 (let a = new A(); a.sayHi();) 的类的实例更新为静态调用 (A.sayHi();)，而不是使用类调用的实例方法
¥Also note in the above examples that if you switch a method to a static method, instances of the class that call the static method (let a = new A(); a.sayHi();) have to be updated to being a static call (A.sayHi();) instead of having the instance of the class call the method
规则详情
¥Rule Details
此规则旨在标记不使用 this 的类方法。
¥This rule is aimed to flag class methods that do not use this.
此规则的错误代码示例：
¥Examples of incorrect code for this rule:
/*eslint class-methods-use-this: "error"*/
class A {
foo() {
console.log("Hello World"); /*error Expected 'this' to be used by class method 'foo'.*/
}
}
此规则的正确代码示例：
¥Examples of correct code for this rule:
/*eslint class-methods-use-this: "error"*/
class A {
foo() {
this.bar = "Hello World"; // OK, this is used
}
}
class B {
constructor() {
// OK. constructor is exempt
}
}
class C {
static foo() {
// OK. static methods aren't expected to use this.
}
static {
// OK. static blocks are exempt.
}
}
选项
¥Options
此规则有两个选项：
¥This rule has two options:
-
"exceptMethods"允许使用此规则忽略指定的方法名称。¥
"exceptMethods"allows specified method names to be ignored with this rule. -
"enforceForClassFields"强制用作实例字段初始值设定项的函数使用this。（默认：true）¥
"enforceForClassFields"enforces that functions used as instance field initializers utilizethis. (default:true)
exceptMethods
"class-methods-use-this": [<enabled>, { "exceptMethods": [<...exceptions>] }]
"exceptMethods" 选项允许你传递要忽略警告的方法名称数组。例如，你可能有来自外部库的规范，要求你将方法覆盖为常规函数（而不是静态方法），并且不使用函数体内的 this。在这种情况下，你可以添加该方法以在警告中忽略。
¥The "exceptMethods" option allows you to pass an array of method names for which you would like to ignore warnings. For example, you might have a spec from an external library that requires you to overwrite a method as a regular function (and not as a static method) and does not use this inside the function body. In this case, you can add that method to ignore in the warnings.
当不使用 "exceptMethods" 时，此规则的错误代码示例：
¥Examples of incorrect code for this rule when used without "exceptMethods":
/*eslint class-methods-use-this: "error"*/
class A {
foo() {
}
}
与 exceptMethods 一起使用时此规则的正确代码示例：
¥Examples of correct code for this rule when used with exceptMethods:
/*eslint class-methods-use-this: ["error", { "exceptMethods": ["foo", "#bar"] }] */
class A {
foo() {
}
#bar() {
}
}
enforceForClassFields
"class-methods-use-this": [<enabled>, { "enforceForClassFields": true | false }]
enforceForClassFields 选项强制用作实例字段初始值设定项的箭头函数和函数表达式使用 this。（默认：true）
¥The enforceForClassFields option enforces that arrow functions and function expressions used as instance field initializers utilize this. (default: true)
使用 { "enforceForClassFields": true } 选项（默认）的此规则的错误代码示例：
¥Examples of incorrect code for this rule with the { "enforceForClassFields": true } option (default):
/*eslint class-methods-use-this: ["error", { "enforceForClassFields": true }] */
class A {
foo = () => {}
}
使用 { "enforceForClassFields": true } 选项（默认）的此规则的正确代码示例：
¥Examples of correct code for this rule with the { "enforceForClassFields": true } option (default):
/*eslint class-methods-use-this: ["error", { "enforceForClassFields": true }] */
class A {
foo = () => {this;}
}
使用 { "enforceForClassFields": false } 选项的此规则的正确代码示例：
¥Examples of correct code for this rule with the { "enforceForClassFields": false } option:
/*eslint class-methods-use-this: ["error", { "enforceForClassFields": false }] */
class A {
foo = () => {}
}
版本
此规则是在 ESLint v3.4.0 中引入。