PropertyDrawer

Base class to derive custom property drawers from. Use this to create custom drawers for your own Serializable classes or for script variables with custom PropertyAttributes.

Note: This is an editor class. To use it you have to place your script in Assets/Editor inside your project folder. Editor classes are in the UnityEditor namespace so for C# scripts you need to add "using UnityEditor;" at the beginning of the script.

PropertyDrawers have two uses:
- Customize the GUI of every instance of a Serializable class.
- Customize the GUI of script members with custom PropertyAttributes.

If you have a custom Serializable class, you can use a PropertyDrawer 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 PropertyDrawer, 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 PropertyDrawer:

Class in the Inspector without and with custom PropertyDrawer.

You can attach the PropertyDrawer 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 ();
    }
}

The other use of PropertyDrawer is to alter the appearance of members in a script that have custom PropertyAttributes. 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 PropertyDrawer 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 the PropertyDrawers are designed to work with LookLikeInspector indentation by default. For now, if you want to use LookLikeControls, please shave off 4 pixels from both left and right side of the provided position:

[CustomPropertyDrawer (typeof (MyClass))]
public class MyDrawer : PropertyDrawer {
    public override void OnGUI (Rect position, SerializedProperty prop, GUIContent label) {
        EditorGUIUtility.LookLikeControls ();
        position.xMin += 4;
        position.xMax -= 4;
        
        // Actual drawing code goes here...
    }
}

See Also: PropertyAttribute class, CustomPropertyDrawer class.

attribute

OnGUI
GetPropertyHeight