Expected 'this' to be used by class method 'renderProgress'. Open
renderProgress(progress) {
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title: class-methods-use-this ruletype: suggestion furtherreading: - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes
- https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/static
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()
)
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"
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"
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
Rule Details
This rule is aimed to flag class methods that do not use this
.
Examples of incorrect code for this rule:
::: incorrect
/*eslint class-methods-use-this: "error"*/
/*eslint-env es6*/
class A {
foo() {
console.log("Hello World"); /*error Expected 'this' to be used by class method 'foo'.*/
}
}
:::
Examples of correct code for this rule:
::: correct
/*eslint class-methods-use-this: "error"*/
/*eslint-env es6*/
class A {
foo() {
this.bar = "Hello World"; // OK, this is used
}
}
class A {
constructor() {
// OK. constructor is exempt
}
}
class A {
static foo() {
// OK. static methods aren't expected to use this.
}
static {
// OK. static blocks are exempt.
}
}
:::
Options
This rule has two options:
-
"exceptMethods"
allows specified method names to be ignored with this rule. -
"enforceForClassFields"
enforces that functions used as instance field initializers utilizethis
. (default:true
)
exceptMethods
"class-methods-use-this": [<enabled>, { "exceptMethods": [<...exceptions>] }]</enabled>
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.
Examples of incorrect code for this rule when used without "exceptMethods"
:
::: incorrect
/*eslint class-methods-use-this: "error"*/
class A {
foo() {
}
}
:::
Examples of correct code for this rule when used with exceptMethods:
::: correct
/*eslint class-methods-use-this: ["error", { "exceptMethods": ["foo", "#bar"] }] */
class A {
foo() {
}
#bar() {
}
}
:::
enforceForClassFields
"class-methods-use-this": [<enabled>, { "enforceForClassFields": true | false }]</enabled>
The enforceForClassFields
option enforces that arrow functions and function expressions used as instance field initializers utilize this
. (default: true
)
Examples of incorrect code for this rule with the { "enforceForClassFields": true }
option (default):
::: incorrect
/*eslint class-methods-use-this: ["error", { "enforceForClassFields": true }] */
class A {
foo = () => {}
}
:::
Examples of correct code for this rule with the { "enforceForClassFields": true }
option (default):
::: correct
/*eslint class-methods-use-this: ["error", { "enforceForClassFields": true }] */
class A {
foo = () => {this;}
}
:::
Examples of correct code for this rule with the { "enforceForClassFields": false }
option:
::: correct
/*eslint class-methods-use-this: ["error", { "enforceForClassFields": false }] */
class A {
foo = () => {}
}
::: Source: http://eslint.org/docs/rules/
Similar blocks of code found in 2 locations. Consider refactoring. Open
<label htmlFor="upload-attachment-all-input" className="btn btn-success btn-xs add">
<span className="btn-label">
<Icon icon="link" /> {t('System', 'Add to all languages')}
</span>
<input
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Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 99.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Similar blocks of code found in 2 locations. Consider refactoring. Open
<label htmlFor="upload-attachment-input" className="btn btn-success btn-xs add">
<span className="btn-label">
<Icon icon="paperclip" /> {t('System', 'Add file')}
</span>
<input
- Read upRead up
Duplicated Code
Duplicated code can lead to software that is hard to understand and difficult to change. The Don't Repeat Yourself (DRY) principle states:
Every piece of knowledge must have a single, unambiguous, authoritative representation within a system.
When you violate DRY, bugs and maintenance problems are sure to follow. Duplicated code has a tendency to both continue to replicate and also to diverge (leaving bugs as two similar implementations differ in subtle ways).
Tuning
This issue has a mass of 99.
We set useful threshold defaults for the languages we support but you may want to adjust these settings based on your project guidelines.
The threshold configuration represents the minimum mass a code block must have to be analyzed for duplication. The lower the threshold, the more fine-grained the comparison.
If the engine is too easily reporting duplication, try raising the threshold. If you suspect that the engine isn't catching enough duplication, try lowering the threshold. The best setting tends to differ from language to language.
See codeclimate-duplication
's documentation for more information about tuning the mass threshold in your .codeclimate.yml
.
Refactorings
- Extract Method
- Extract Class
- Form Template Method
- Introduce Null Object
- Pull Up Method
- Pull Up Field
- Substitute Algorithm
Further Reading
- Don't Repeat Yourself on the C2 Wiki
- Duplicated Code on SourceMaking
- Refactoring: Improving the Design of Existing Code by Martin Fowler. Duplicated Code, p76
Definition for rule 'node/no-restricted-import' was not found. Open
import PropTypes from 'prop-types';
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propType "languages" is not required, but has no corresponding defaultProps declaration. Open
languages: PropTypes.object,
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Export statements should appear at the end of the file Open
export class UploadAttachment extends Component {
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propType "uploadAttachment" is not required, but has no corresponding defaultProps declaration. Open
uploadAttachment: PropTypes.func,
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A control must be associated with a text label. Open
<input
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A control must be associated with a text label. Open
<input
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For more information visit Source: http://eslint.org/docs/rules/
Prop type "object" is forbidden Open
languages: PropTypes.object,
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propType "storeKey" is not required, but has no corresponding defaultProps declaration. Open
storeKey: PropTypes.string,
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propType "progress" is not required, but has no corresponding defaultProps declaration. Open
progress: PropTypes.object,
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For more information visit Source: http://eslint.org/docs/rules/
Prefer named exports. Open
export default connect(mapStateToProps, mapDispatchToProps)(UploadAttachment);
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Prop type "object" is forbidden Open
progress: PropTypes.object,
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propType "entity" is not required, but has no corresponding defaultProps declaration. Open
entity: PropTypes.string,
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For more information visit Source: http://eslint.org/docs/rules/