---
sidebar_position: 6
title: Automatically Actions
---
# Automatically Generated Actions

In the [Quick Start](/guides/topic-detail/model/quick-start), we implemented the simplest counter model, which still required 10 lines of code. In fact, Modern.js supports automatically generating commonly used actions based on the declared `state` type, which reduces the amount of boilerplate code. The currently supported types are:

- Primitive data types
- Array types
- Simple object types (Plain Object)

## Primitive data types

```ts
const countModel = model('count').define({ state: 1 });
```

As shown above, we only need one line to create a simple `countModel`. Here's an example code that uses the model:

```tsx
function Counter() {
  const [state, actions] = useModel(countModel);

  useEffect(() => {
    // 增加 1
    actions.setState(state + 1);
  }, []);
}
```

## Array Types

When the state is an array type, an example code for automatically generating actions is shown below:

```ts
const countModel = model('count').define({ state: [] });

function Counter() {
  const [state, actions] = useModel(countModel);

  useEffect(() => {
    actions.push(1);
    actions.pop();
    actions.shift();
    actions.unshift(1);
    actions.concat([1]);
    actions.splice(0, 1, 2);
    actions.filter(value => value > 1);
  }, []);
}
```

We can use the methods of the JavaScript Array object to modify the state.

## Simple Object Types

When the state is a simple object type, an example code for automatically generating actions is shown below:

```ts
const countModel = model('count').define({
  state: {
    a: 1,
    b: [],
    c: {},
  },
});

function Counter() {
  const [state, actions] = useModel(countModel);

  useEffect(() => {
    actions.setA(2);
    actions.setB([1]);
    actions.setC({ a: 1 });
  }, []);
}
```

Three different fields `a`, `b`, and `c` each generate `setA`, `setB`, and `setC` actions, respectively.

:::info
When the user-defined action and the action automatically generated by Modern.js have the same name, the user-defined action takes precedence. For example, if `setA` action is already defined in `countModel`, calling `actions.setA()` executes the user-defined `setA`.
:::

:::info Additional Information
For more information on related APIs, please refer to [here](/apis/app/runtime/model/auto-actions).
:::

