Reference Manual>Extending the Editor>Property Drawers
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Property Drawers

Property Drawers can be used to customize the look of certain controls in the Inspector, by using attributes on your scripts, or by controlling how a specific Serializable class should look.

Property Drawers have two uses:

Customize the GUI of a Serializable class

If you have a custom Serializable class, you can use a Property Drawer to control how it looks in the Inspector. Consider the Serializable class Ingredient in the script below: 

// Recipe.js
// This is not an editor script

enum IngredientUnit { Spoon, Cup, Bowl, Piece }

// Custom serializable class
class Ingredient extends System.Object {
	var name : String;
	var amount : int = 1;
	var unit : IngredientUnit;
}

var potionResult : Ingredient;
var potionIngredients : Ingredient[];

function Update () {
	// Update logic here...
}

Using a custom Property Drawer, every appearance of the Ingredient class in the Inspector can be changed. Compare the look of the Ingredient properties in the Inspector without and with a custom Property Drawer:

Class in the Inspector without (left) and with (right) custom Property Drawer.

You can attach the Property Drawer to a Serializable class by using the CustomPropertyDrawer attribute and pass in the type of the Serializable class that it's a drawer for. 

// IngredientDrawer.js
@CustomPropertyDrawer (Ingredient)
class IngredientDrawer extends PropertyDrawer {

	// Draw the property inside the given rect
	function OnGUI (position : Rect, property : SerializedProperty, label : GUIContent) {
		// Using BeginProperty / EndProperty on the parent property means that
		// prefab override logic works on the entire property.
		EditorGUI.BeginProperty (position, label, property);

		// Draw label
		position = EditorGUI.PrefixLabel (position, GUIUtility.GetControlID (FocusType.Passive), label);

		// Don't make child fields be indented
		var indent = EditorGUI.indentLevel;
		EditorGUI.indentLevel = 0;

		// Calculate rects
		var amountRect = new Rect (position.x, position.y, 30, position.height);
		var unitRect = new Rect (position.x+35, position.y, 50, position.height);
		var nameRect = new Rect (position.x+90, position.y, position.width-90, position.height);

		// Draw fields - passs GUIContent.none to each so they are drawn without labels
		EditorGUI.PropertyField (amountRect, property.FindPropertyRelative ("amount"), GUIContent.none);
		EditorGUI.PropertyField (unitRect, property.FindPropertyRelative ("unit"), GUIContent.none);
		EditorGUI.PropertyField (nameRect, property.FindPropertyRelative ("name"), GUIContent.none);

		// Set indent back to what it was
		EditorGUI.indentLevel = indent;

		EditorGUI.EndProperty ();
	}
}

Customize the GUI of script members using Property Attributes

The other use of Property Drawer is to alter the appearance of members in a script that have custom Property Attributes. Say you want to limit floats or integers in your script to a certain range and show them as sliders in the Inspector. Using the built-in PropertyAttribute called RangeAttribute you can do just that: 

// Show this float in the Inspector as a slider between 0 and 10
@Range (0.0, 10.0)
var myFloat = 0.0;

You can make your own PropertyAttribute as well. We'll use the code for the RangeAttribute as an example. The attribute must extend the PropertyAttribute class. If you want, your property can take parameters and store them as public member variables. 

// This is not an editor script. The property attribute class should be placed in a regular script file.
class RangeAttribute extends PropertyAttribute {
	var min : float;
	var max : float;

	function RangeAttribute (min : float, max : float) {
		this.min = min;
		this.max = max;
	}
}

Now that you have the attribute, you need to make a Property Drawer that draws properties that have that attribute. The drawer must extend the PropertyDrawer class, and it must have a CustomPropertyDrawer attribute to tell it which attribute it's a drawer for. 

// The property drawer class should be placed in an editor script, inside a folder called Editor.

// Tell the RangeDrawer that it is a drawer for properties with the RangeAttribute.
@CustomPropertyDrawer (RangeAttribute)
class RangeDrawer extends PropertyDrawer {

	// Draw the property inside the given rect
	function OnGUI (position : Rect, property : SerializedProperty, label : GUIContent) {

		// First get the attribute since it contains the range for the slider
		var range : RangeAttribute = attribute as RangeAttribute;

		// Now draw the property as a Slider or an IntSlider based on whether it's a float or integer.
		if (property.propertyType == SerializedPropertyType.Float)
			EditorGUI.Slider (position, property, range.min, range.max, label);
		else if (property.propertyType == SerializedPropertyType.Integer)
			EditorGUI.IntSlider (position, property, range.min, range.max, label);
		else
			EditorGUI.LabelField (position, label.text, "Use Range with float or int.");
	}
}

Note that for performance reasons, EditorGUILayout functions are not usable with Property Drawers.

Page last updated: 2013-08-15

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