Version: 2017.2 (switch to 2017.3b)
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Property Drawers

Property Drawers can be used to customize the look of certain controls in the Inspector window 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 every instance of a Serializable class.
  • Customize the GUI of script members with custom Property Attributes.

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 examples below (Note: These are not editor scripts. Property attribute classes should be placed in a regular script file):

JavaScript (example):

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...
}

C# (example):


using UnityEngine;
using System.Collections;

public enum IngredientUnit { Spoon, Cup, Bowl, Piece }

// Custom serializable class
[System.Serializable]
public class Ingredient : System.Object {
    string name;
    int amount = 1;
    IngredientUnit unit;
}

public class Recipe : MonoBehaviour {
    Ingredient potionResult;
    Ingredient[] potionIngredients;

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

using UnityEngine;
using System.IO;

class Testing : MonoBehaviour{

    enum IngredientUnit { Spoon, Cup, Bowl, Piece }

    // Custom serializable class
    [System.Serializable]
    class Ingredient{
        string name;
        int amount = 1;
        IngredientUnit unit;
    }

    Ingredient potionResult;
    Ingredient[] potionIngredients;

    void 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.
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.

JavaScript (example):

@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 ();
    }
}

C# (examples):

using UnityEngine;
using UnityEditor;
using System.Collections;

[CustomPropertyDrawer(typeof(Ingredient))]
public class IngredientDrawer : PropertyDrawer {

    // Draw the property inside the given rect
    void OnGUI(Rect position, SerializedProperty property, GUIContent label) {
        // 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
        int indent = EditorGUI.indentLevel;
        EditorGUI.indentLevel = 0;

        // Calculate rects
        Rect amountRect = new Rect(position.x, position.y, 30, position.height);
        Rect unitRect = new Rect(position.x+35, position.y, 50, position.height);
        Rect 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();
    }
}

using UnityEngine;
using UnityEditor;
using System.Collections;


[CustomPropertyDrawer (Ingredient)]
class IngredientDrawer : PropertyDrawer {
    
    // Draw the property inside the given rect
    void OnGUI (Rect position, SerializedProperty property, GUIContent label) {
        // 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
        Rect amountRect = new Rect (position.x, position.y, 30, position.height);
        Rect unitRect = new Rect (position.x+35, position.y, 50, position.height);
        Rect 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:

JavaScript (example):

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

//C# example.
[Range(0.0f, 10.0f)]
public float myFloat = 0.0f;

C# (example):

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

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.

JavaScript (example):

class RangeAttribute extends PropertyAttribute {
    var min : float;
    var max : float;
    
    function RangeAttribute (min : float, max : float) {
        this.min = min;
        this.max = max;
    }
}

C# (examples):

using UnityEngine;
using System.Collections;


public class RangeAttribute : PropertyAttribute {
    public float min;
    public float max;

    public RangeAttribute (float min, float max) {
        this.min = min;
        this.max = max;
    }
}
using UnityEngine;
using System.Collections;

public class Testing : PropertyAttribute 
{
        float min;
        float max;
        
        void RangeAttribute (float min, float max) {
            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.

JavaScript (example):

// 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.");
    }
}

C# (examples):

using UnityEngine;
using UnityEditor;
using System.Collections;

// Tell the RangeDrawer that it is a drawer for properties with the RangeAttribute.

[CustomPropertyDrawer(typeof(RangeAttribute))]
public class RangeDrawer : PropertyDrawer {

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

        // First get the attribute since it contains the range for the slider
        RangeAttribute range  = 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, (int) range.min, (int) 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.

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