# Attribute Modifier

With the attribute modifier, you can dynamically set component attributes, complete with the **if/else** syntax and polymorphic style.

>  **NOTE**
>
>  This feature is supported since API version 11. Updates will be marked with a superscript to indicate their earliest API version.
>
> Ensure that the attributes set in **attributeModifier** are different from those set in other methods. Otherwise, **attributeModifier** does not take effect when the page is refreshed.

## attributeModifier

attributeModifier(modifier: AttributeModifier\<T>)

Creates an attribute modifier.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.ArkUI.ArkUI.Full

**Parameters**

| Name  | Type                 | Mandatory| Description                                                        |
| -------- | --------------------- | ---- | ------------------------------------------------------------ |
| modifier | [AttributeModifier\<T>](#attributemodifiert) | Yes  | Modifier for dynamically setting attributes on the current component. The **if/else** syntax is supported.<br>**modifier**: attribute modifier. You need a custom class to implement the **AttributeModifier** API.|

## AttributeModifier\<T>

You need a custom class to implement the **AttributeModifier** API.

**Atomic service API**: This API can be used in atomic services since API version 12.

### applyNormalAttribute
applyNormalAttribute(instance: T) : void

Applies the style of a component in the normal state.

**Atomic service API**: This API can be used in atomic services since API version 12.

### applyPressedAttribute
applyPressedAttribute(instance: T) : void

Applies the style of a component in the pressed state.

**Atomic service API**: This API can be used in atomic services since API version 12.

### applyFocusedAttribute
applyFocusedAttribute(instance: T) : void

Applies the style of a component in the focused state.

**Atomic service API**: This API can be used in atomic services since API version 12.

### applyDisabledAttribute
applyDisabledAttribute(instance: T) : void

Applies the style of a component in the disabled state.

**Atomic service API**: This API can be used in atomic services since API version 12.

### applySelectedAttribute
applySelectedAttribute(instance: T) : void

Applies the style of a component in the selected state.

In the preceding APIs, **instance** indicates the component type. You can customize these APIs and use them with the **if/else **syntax.

**Atomic service API**: This API can be used in atomic services since API version 12.

**Parameters**

| Name            | Description                                                        |
| -------------------- | ------------------------------------------------------------ |
| instance |Component attribute class, which identifies the type of component to which attributes will be applied, for example, **ButtonAttribute** for the **\<Button>** component and **TextAttribute** for the **\<Text>** component.|

**Value range of the instance parameter**

AlphabetIndexerAttribute, BadgeAttribute, BlankAttribute, ButtonAttribute, CalendarPickerAttribute, CanvasAttribute, CheckboxAttribute, CheckboxGroupAttribute, CircleAttribute, ColumnAttribute, ColumnSplitAttribute, ShapeAttribute, CommonAttribute, CounterAttribute, DataPanelAttribute, DatePickerAttribute, DividerAttribute, EllipseAttribute, FlexAttribute, FlowItemAttribute, FormLinkAttribute, GaugeAttribute, GridAttribute, GridColAttribute, ColumnAttribute, GridItemAttribute, GridRowAttribute, HyperlinkAttribute, ImageAttribute, ImageAnimatorAttribute, ImageSpanAttribute, LineAttribute, ListAttribute, ListItemAttribute, ListItemGroupAttribute, LoadingProgressAttribute, MarqueeAttribute, MenuAttribute, MenuItemAttribute, MenuItemGroupAttribute, NavDestinationAttribute, NavigationAttribute, NavigatorAttribute, NavRouterAttribute, PanelAttribute, PathAttribute, PatternLockAttribute, PolygonAttribute, PolylineAttribute, ProgressAttribute, QRCodeAttribute, RadioAttribute, RatingAttribute, RectAttribute, RefreshAttribute, RelativeContainerAttribute, RichEditorAttribute, RichTextAttribute, RowAttribute, RowSplitAttribute, ScrollAttribute, ScrollBarAttribute, SearchAttribute, SelectAttribute, ShapeAttribute, SideBarContainerAttribute, SliderAttribute, SpanAttribute, StackAttribute, StepperAttribute, StepperItemAttribute, SwiperAttribute, SymbolGlyphAttribute, TabContentAttribute, TabsAttribute, TextAttribute, TextAreaAttribute, TextClockAttribute, TextInputAttribute, TextPickerAttribute, TextTimerAttribute, TimePickerAttribute, ToggleAttribute, VideoAttribute, WaterFlowAttribute, XComponentAttribute, ParticleAttribute<!--Del-->, EffectComponentAttribute, FormComponentAttribute, PluginComponentAttribute, RemoteWindowAttribute, UIExtensionComponentAttribute<!--DelEnd-->

**Supported attributes**

Attributes whose input parameters are [CustomBuilder](ts-types.md#custombuilder8) or lamda expressions are not supported. In addition, gestures are not supported. Only the following events are supported: **onClick**, **onTouch**, **onAppear**, **onDisAppear**, **onMouse**, **onHover**, **onKeyEvent**, **onBlur**, **onFocus**, **onAreaChange**, **onSizeChange**, and **onGestureJudgeBegin**. Deprecated attributes are not supported. When an attribute not supported is used, the exception "Method not implemented " is thrown.
## Custom Modifier
Custom modifiers can be used in building components and configuring attributes since API version 12. Through the custom modifiers, you can call the attribute and style APIs of encapsulated components.

**Supported custom modifiers** 

CommonModifier, ColumnModifier, ColumnSplitModifier, RowModifier, RowSplitModifier, SideBarContainerModifier, BlankModifier, DividerModifier, GridColModifier, GridRowModifier, NavDestinationModifier, NavigatorModifier, StackModifier, NavigationModifier, NavRouterModifier, StepperItemModifier, TabsModifier, GridModifier, GridItemModifier, ListModifier, ListItemModifier, ListItemGroupModifier, ScrollModifier, SwiperModifier, WaterFlowModifier, ButtonModifier, CounterModifier, TextPickerModifier, TimePickerModifier, ToggleModifier, CalendarPickerModifier, CheckboxModifier, CheckboxGroupModifier, DatePickerModifier, RadioModifier, RatingModifier, SelectModifier, SliderModifier, PatternLockModifier, SpanModifier, RichEditorModifier, RefreshModifier, SearchModifier, TextAreaModifier, TextModifier, TextInputModifier, ImageSpanModifier, ImageAnimatorModifier, ImageModifier, VideoModifier, DataPanelModifier, GaugeModifier, LoadingProgressModifier, MarqueeModifier, ProgressModifier, QRCodeModifier, TextClockModifier, TextTimerModifier, LineModifier, PathModifier, PolygonModifier, PolylineModifier, RectModifier, ShapeModifier, AlphabetIndexerModifier, FormComponentModifier, HyperlinkModifier, MenuModifier, MenuItemModifier, PanelModifier, SymbolGlyphModifier, ParticleModifier 
**CommonModifier** can be used for unexposed components.

**Precautions**
1. When a custom modifier is applied to a component, the corresponding attribute of the component takes effect. 
2. Updating the attribute value of a custom modifier changes the corresponding attribute of the component to which the modifier is applied. The custom modifier is a base class, and the constructed object is a child class object. When using the object, use **as** to assert the type as a child class. 
3. With a custom modifier applied to two components, updating the attribute value of the custom modifier changes the corresponding attributes of both components. 
4. If attributes A and B are set through a custom modifier, and then attributes C and D are set through other means, all the four attributes take effect on the component. 
5. The custom modifier does not support change observation for @State decorated variables. For details, see Example 2. 
6. If you use **attributeModifier** to set attributes multiple times, all the set attributes take effect, and those attributes that are set multiple times take effect based on the configuration sequence.  

## Example
### Example 1
```ts
// xxx.ets
class MyButtonModifier implements AttributeModifier<ButtonAttribute> {
  isDark: boolean = false
  applyNormalAttribute(instance: ButtonAttribute): void {
    if (this.isDark) {
      instance.backgroundColor(Color.Black)
    } else {
      instance.backgroundColor(Color.Red)
    }
  }
}

@Entry
@Component
struct attributeDemo {
  @State modifier: MyButtonModifier = new MyButtonModifier()

  build() {
    Row() {
      Column() {
        Button("Button")
          .attributeModifier(this.modifier)
          .onClick(() => {
            this.modifier.isDark = !this.modifier.isDark
          })
      }
      .width('100%')
    }
    .height('100%')
  }
}
```
![attributeModifier_ifelse](figures/attributeModifier_ifelse.gif)



```ts
// xxx.ets
class MyButtonModifier implements AttributeModifier<ButtonAttribute> {
  applyNormalAttribute(instance: ButtonAttribute): void {
    instance.backgroundColor(Color.Black)
  }

  applyPressedAttribute(instance: ButtonAttribute): void {
    instance.backgroundColor(Color.Red)
  }
}

@Entry
@Component
struct attributePressedDemo {
  @State modifier: MyButtonModifier = new MyButtonModifier()

  build() {
    Row() {
      Column() {
        Button("Button")
          .attributeModifier(this.modifier)
      }
      .width('100%')
    }
    .height('100%')
  }
}
```
![attributeModifier_ifelse](figures/attributeModifier_ifelse.gif)

### Example 2
The custom modifier does not support change observation for @State decorated variables.
```ts
import { CommonModifier } from "@kit.ArkUI"

class MyModifier extends CommonModifier {
  applyNormalAttribute(instance: CommonAttribute) : void{
    super.applyNormalAttribute?.(instance);
  }
}

@Component
struct MyImage1 {
  @Link modifier : CommonModifier

  build(){
    Image($r("app.media.testImage")).attributeModifier(this.modifier as MyModifier)
  }
}
@Entry
@Component
struct Index {
  index : number = 0;
  @State width1 : number = 100;
  @State height1 : number = 100;
  @State myModifier: CommonModifier = new MyModifier().width(this.width1).height(this.height1).margin(10)

  build() {
    Column() {
      Button($r("app.string.EntryAbility_label"))
        .margin(10)
        .onClick(() => {
          console.log("Modifier","onClick")
          this.index ++;
          if(this.index %2 === 1){
            this.width1 = 10;
            console.log("Modifier","setGroup1")
          }else{
            this.width1 = 10;
            console.log("Modifier","setGroup2")
          }
        })
      MyImage1({modifier:this.myModifier})
    }
    .width('100%')
  }
}
```
![attributeModifier2](figures/attributeModifier2.gif)  
### Example 3
In this example, the custom modifier sets the **width** and **height** attributes, and the **borderStyle** and **borderWidth** attributes are set through a button click. In this case, all the four attributes take effect when the button is clicked.
```ts
import { CommonModifier } from "@kit.ArkUI"

class MyModifier extends CommonModifier {
  applyNormalAttribute(instance: CommonAttribute) : void{
    super.applyNormalAttribute?.(instance);
  }

  public setGroup1() : void {
    this.borderStyle(BorderStyle.Dotted)
    this.borderWidth(8)
  }

  public setGroup2() : void {
    this.borderStyle(BorderStyle.Dashed)
    this.borderWidth(8)
  }
}

@Component
struct MyImage1 {
  @Link modifier : CommonModifier

  build(){
    Image($r("app.media.testImage")).attributeModifier(this.modifier as MyModifier)
  }
}

@Entry
@Component
struct Index {
  @State myModifier: CommonModifier = new MyModifier().width(100).height(100).margin(10)
  index : number = 0;

  build() {
    Column() {
      Button($r("app.string.EntryAbility_label"))
        .margin(10)
        .onClick(() => {
          console.log("Modifier","onClick")
          this.index ++;
          if(this.index %2 === 1){
            (this.myModifier as MyModifier).setGroup1()
            console.log("Modifier","setGroup1")
          }else{
            (this.myModifier as MyModifier).setGroup2()
            console.log("Modifier","setGroup2")
          }
        })
      MyImage1({modifier:this.myModifier})
    }
    .width('100%')
  }
}
```
![attributeModifier](figures/attributeModifier.gif)