---
url: /rules/no-mutable-public-property-of-construct.md
---

# no-mutable-public-property-of-construct

This rule disallows making `public` properties of a CDK Construct mutable (i.e. disallow defining `public` properties without the `readonly` modifier).

Constructs often represent stateful AWS resources.
Making these `public` properties `readonly` helps prevent unintended modifications after the Construct has been instantiated, leading to more predictable and maintainable code.

Therefore, it is recommended to specify the `readonly` modifier for `public` properties.

(This rule applies only to classes that extends from `Construct` or `Stack`.)

***

#### 🔧 How to use

::: code-group

```ts [Oxlint]
// oxlint.config.ts
export default defineConfig({
  // ... some configs
  rules: {
    "awscdk/no-mutable-public-property-of-construct": "error",
  },
});
```

```js [ESLint]
// eslint.config.mjs
export default defineConfig({
  // ... some configs
  rules: {
    "awscdk/no-mutable-public-property-of-construct": "error",
  },
});
```

:::

#### ✅ Correct Example

```ts
import { Construct } from "constructs";
import { IBucket } from "aws-cdk-lib/aws-s3";

export class MyConstruct extends Construct {
  // ✅ public readonly properties are allowed
  public readonly bucket: IBucket;
}
```

#### ❌ Incorrect Example

```ts
import { Construct } from "constructs";
import { IBucket } from "aws-cdk-lib/aws-s3";

export class MyConstruct extends Construct {
  // ❌ public properties should be readonly
  public bucket: IBucket;
}
```