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# HasPrefixElement

> Interface for Vaadin components that support prefix slot content

## Overview

`HasPrefixElement` provides utilities to interact with Vaadin components that implement the `HasPrefix` interface, which allows placing content in a `prefix` slot. The prefix typically appears at the start of the component, before the main input or content area.

This mixin interface extends [HasLocatorElement](/api/shared/has-locator) and provides default implementations for accessing, reading, and asserting prefix slot content.

## Interface

```java theme={null}
public interface HasPrefixElement extends HasLocatorElement {
    default Locator getPrefixLocator() { ... }
    default String getPrefixText() { ... }
    default void assertPrefixHasText(String text) { ... }
}
```

## Methods

### getPrefixLocator()

Returns a locator for the prefix slot content.

```java theme={null}
default Locator getPrefixLocator()
```

**Returns:** `Locator` targeting the first element with `slot="prefix"`

**Implementation:**

```java theme={null}
return getLocator().locator("*[slot=\"prefix\"]").first();
```

***

### getPrefixText()

Retrieves the text content of the prefix slot.

```java theme={null}
default String getPrefixText()
```

**Returns:** The text content of the prefix element

***

### assertPrefixHasText()

Asserts that the prefix slot has the expected text, or is hidden when null.

```java theme={null}
default void assertPrefixHasText(String text)
```

<ParamField path="text" type="String">
  Expected text content of the prefix. If `null`, asserts that the prefix is not visible.
</ParamField>

**Behavior:**

* If `text` is non-null: Asserts the prefix has exactly that text
* If `text` is null: Asserts the prefix is not visible

## Implementing Classes

The following element classes implement `HasPrefixElement`:

* `TextFieldElement` - Text input fields
* `BigDecimalFieldElement` - Decimal number fields
* `AbstractNumberFieldElement` - Base class for number fields
* `ComboBoxElement` - Combo box selectors
* `SelectElement` - Select dropdowns
* `ButtonElement` - Action buttons
* `SideNavigationItemElement` - Navigation items

## Usage Examples

### Basic Prefix Access

```java theme={null}
import com.microsoft.playwright.Page;
import org.vaadin.addons.dramafinder.element.TextFieldElement;

public class PrefixExample {
    public void testPrefixContent(Page page) {
        TextFieldElement emailField = TextFieldElement.getByLabel(page, "Email");
        
        // Get the prefix text
        String prefixText = emailField.getPrefixText();
        System.out.println("Prefix: " + prefixText);
        
        // Assert the prefix displays an icon or text
        emailField.assertPrefixHasText("@");
    }
}
```

### Custom Prefix Interactions

```java theme={null}
public class CustomPrefixExample {
    public void clickPrefixIcon(Page page) {
        TextFieldElement searchField = TextFieldElement.getByLabel(page, "Search");
        
        // Access the prefix locator for custom interactions
        Locator prefixIcon = searchField.getPrefixLocator();
        
        // Click on an interactive prefix element (e.g., a search icon)
        prefixIcon.click();
    }
}
```

### Asserting Prefix Visibility

```java theme={null}
public class PrefixVisibilityExample {
    public void testPrefixVisibility(Page page) {
        TextFieldElement phoneField = TextFieldElement.getByLabel(page, "Phone");
        
        // Assert prefix is present with text
        phoneField.assertPrefixHasText("+1");
        
        // After clearing or some action, assert prefix is hidden
        phoneField.assertPrefixHasText(null);
    }
}
```

### Integration Test Example

```java theme={null}
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;

public class TextFieldPrefixIT {
    @Test
    public void shouldDisplayCurrencyPrefix() {
        TextFieldElement priceField = TextFieldElement.getByLabel(page, "Price");
        
        // Verify the currency symbol appears as a prefix
        assertEquals("$", priceField.getPrefixText());
        
        // Assert using the built-in assertion method
        priceField.assertPrefixHasText("$");
    }
    
    @Test
    public void shouldHidePrefixWhenNotSet() {
        TextFieldElement plainField = TextFieldElement.getByLabel(page, "Plain Input");
        
        // Assert no prefix is visible
        priceField.assertPrefixHasText(null);
    }
}
```

## Related Interfaces

* [HasLocatorElement](/api/shared/has-locator) - Parent interface
* [HasSuffixElement](/api/shared/has-suffix) - Companion interface for suffix slot content

## Vaadin Documentation

For more information about the Vaadin `HasPrefix` interface, see the [Vaadin Components documentation](https://vaadin.com/docs/latest/components).