Property Drawer for Unity used to show or hide the Field depending on certain conditions

example.gif

ShowWhenAttribute.cs

// DONT PUT IN EDITOR FOLDER

using System;
using UnityEngine;

/// <summary>
/// Attribute used to show or hide the Field depending on certain conditions
/// </summary>
[AttributeUsage(AttributeTargets.Field, AllowMultiple = false, Inherited = true)]
public class ShowWhenAttribute : PropertyAttribute {

	public readonly string conditionFieldName;
	public readonly object comparationValue;
	public readonly object[] comparationValueArray;
	
	/// <summary>
	/// Attribute used to show or hide the Field depending on certain conditions
	/// </summary>
	/// <param name="conditionFieldName">Name of the bool condition Field</param>
	public ShowWhenAttribute(string conditionFieldName)
	{
		this.conditionFieldName = conditionFieldName;
	}
	
	/// <summary>
	/// Attribute used to show or hide the Field depending on certain conditions
	/// </summary>
	/// <param name="conditionFieldName">Name of the Field to compare (bool, enum, int or float)</param>
	/// <param name="comparationValue">Value to compare</param>
	public ShowWhenAttribute(string conditionFieldName, object comparationValue = null)
	{
		this.conditionFieldName = conditionFieldName;
		this.comparationValue = comparationValue;
	}
	
	/// <summary>
	/// Attribute used to show or hide the Field depending on certain conditions
	/// </summary>
	/// <param name="conditionFieldName">Name of the Field to compare (bool, enum, int or float)</param>
	/// <param name="comparationValueArray">Array of values to compare (only for enums)</param>
	public ShowWhenAttribute(string conditionFieldName, object[] comparationValueArray = null)
	{
		this.conditionFieldName = conditionFieldName;
		this.comparationValueArray = comparationValueArray;
	}
}

ShowWhenDrawer.cs

// PUT IN EDITOR FOLDER

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using UnityEngine;
using UnityEditor;

[CustomPropertyDrawer(typeof(ShowWhenAttribute))]
public class ShowWhenDrawer : PropertyDrawer
{
    private bool showField = true;
    
    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        ShowWhenAttribute attribute = (ShowWhenAttribute) this.attribute;
        SerializedProperty conditionField = property.serializedObject.FindProperty(attribute.conditionFieldName);

        // We check that exist a Field with the parameter name
        if (conditionField == null)
        {
            ShowError(position, label, "Error getting the condition Field. Check the name.");
            return;
        }
        
        switch (conditionField.propertyType)
        {
            case SerializedPropertyType.Boolean:
                try
                {
                    bool comparationValue = attribute.comparationValue == null || (bool)attribute.comparationValue;
                    showField = conditionField.boolValue == comparationValue;
                }
                catch
                {
                    ShowError(position, label, "Invalid comparation Value Type");
                    return;
                }
                break;
            case SerializedPropertyType.Enum:
                object paramEnum = attribute.comparationValue;
                object[] paramEnumArray = attribute.comparationValueArray;
                
                if ( paramEnum == null && paramEnumArray == null)
                {
                    ShowError(position, label, "The comparation enum value is null");
                    return;
                }
                else if (IsEnum(paramEnum))
                {
                    if (!CheckSameEnumType(new[] {paramEnum.GetType()}, property.serializedObject.targetObject.GetType(), conditionField.propertyPath))
                    {
                        ShowError(position, label, "Enum Types doesn't match");
                        return;
                    }
                    else
                    {
                        string enumValue = Enum.GetValues(paramEnum.GetType()).GetValue(conditionField.enumValueIndex).ToString();
                        if (paramEnum.ToString() != enumValue)
                            showField = false;
                        else
                            showField = true;    
                    }                   
                }
                else if (IsEnum(paramEnumArray))
                {
                    if (!CheckSameEnumType(paramEnumArray.Select(x => x.GetType()), property.serializedObject.targetObject.GetType(), conditionField.propertyPath))
                    {
                        ShowError(position, label, "Enum Types doesn't match");
                        return;
                    }
                    else
                    {
                        string enumValue = Enum.GetValues(paramEnumArray[0].GetType()).GetValue(conditionField.enumValueIndex).ToString();
                        if (paramEnumArray.All(x => x.ToString() != enumValue))
                            showField = false;
                        else
                            showField = true;
                    }
                }
                else
                {
                    ShowError(position, label, "The comparation enum value is not an enum");
                    return;
                }
                break;
            case SerializedPropertyType.Integer: 
            case SerializedPropertyType.Float:
                string stringValue;
                bool error = false;

                float conditionValue = 0;
                if (conditionField.propertyType == SerializedPropertyType.Integer)
                    conditionValue = conditionField.intValue;
                else if (conditionField.propertyType == SerializedPropertyType.Float)
                    conditionValue = conditionField.floatValue;
                
                try
                {
                    stringValue = (string)attribute.comparationValue;
                }
                catch
                {
                    ShowError(position, label, "Invalid comparation Value Type");
                    return;
                }

                if (stringValue.StartsWith("=="))
                {
                    float? value = GetValue(stringValue, "==");
                    if (value == null)
                        error = true;
                    else
                        showField = conditionValue == value;
                }
                else if (stringValue.StartsWith("!="))
                {
                    float? value = GetValue(stringValue, "!=");
                    if (value == null)
                        error = true;
                    else
                        showField = conditionValue != value;
                }
                else if (stringValue.StartsWith("<="))
                {
                    float? value = GetValue(stringValue, "<=");
                    if (value == null)
                        error = true;
                    else
                        showField = conditionValue <= value;
                }
                else if (stringValue.StartsWith(">="))
                {
                    float? value = GetValue(stringValue, ">=");
                    if (value == null)
                        error = true;
                    else
                        showField = conditionValue >= value;
                }
                else if (stringValue.StartsWith("<"))
                {
                    float? value = GetValue(stringValue, "<");
                    if (value == null)
                        error = true;
                    else
                        showField = conditionValue < value;
                }
                else if (stringValue.StartsWith(">"))
                {
                    float? value = GetValue(stringValue, ">");
                    if (value == null)
                        error = true;
                    else
                        showField = conditionValue > value;
                }
                
                if (error)
                {
                    ShowError(position, label, "Invalid comparation instruction for Int or float value");
                    return;
                }
                break;
            default:
                ShowError(position, label, "This type has not supported.");
                return;
        }
        
        if (showField)
            EditorGUI.PropertyField(position, property, true);
    }
    
    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
    {
        if (showField)
            return EditorGUI.GetPropertyHeight(property);
        else
            return -EditorGUIUtility.standardVerticalSpacing;
    }

    /// <summary>
    /// Return if the object is enum and not null
    /// </summary>
    private static bool IsEnum(object obj)
    {
        return obj != null && obj.GetType().IsEnum;
    }
    
    /// <summary>
    /// Return if all the objects are enums and not null
    /// </summary>
    private static bool IsEnum(object[] obj)
    {
        return obj != null && obj.All(o => o.GetType().IsEnum);
    }

    /// <summary>
    /// Check if the field with name "fieldName" has the same class as the "checkTypes" classes through reflection
    /// </summary>
    private static bool CheckSameEnumType(IEnumerable<Type> checkTypes, Type classType, string fieldName)
    {
        FieldInfo memberInfo;
        string[] fields = fieldName.Split('.');
        if (fields.Length > 1)
        {
            memberInfo = classType.GetField(fields[0]);
            for (int i = 1; i < fields.Length; i++)
            {
                memberInfo = memberInfo.FieldType.GetField(fields[i]);
            }
        }
        else
            memberInfo = classType.GetField(fieldName);
        
        if (memberInfo != null)
            return checkTypes.All(x => x == memberInfo.FieldType);

        return false;
    }

    private void ShowError(Rect position, GUIContent label, string errorText)
    {
        EditorGUI.LabelField(position, label, new GUIContent(errorText));
        showField = true;
    }

    /// <summary>
    /// Return the float value in the content string removing the remove string
    /// </summary>
    private static float? GetValue(string content, string remove)
    {
        string removed = content.Replace(remove, "");
        try
        {
            return float.Parse(removed);
        }
        catch
        {
            return null;
        }
    }
}

ShowWhenExample.cs

using System;
using UnityEngine;

public class ShowWhenExample : MonoBehaviour
{
    #region Bool Region

    [Header("Check with BOOL")]
    public bool show;
    
    [ShowWhen("show")]
    public float numberWhenTrue;

    [ShowWhen("show", false)]
    public Vector3 vector3WhenFalse;

    [ShowWhen("show")]
    public float[] arrayWhenTrue = {1, 2, 3};

    [Serializable]
    public class ArrayClass
    {
        public Color[] colorArray = {Color.red, Color.blue, Color.green};
    }

    [ShowWhen("show")]
    public ArrayClass workaroundForArrayWhenTrue;

    [Serializable]
    public class CustomClass
    {
        public float floatValue = 99;
        public string stringValue = "string";
    }

    [ShowWhen("show", true)]
    public CustomClass customClass;
  
    [ShowWhen("show", "error")]
    public string stringErrorComparationValueType;

    #endregion

    #region Enum Region

    public enum EaseType
    {
        Linear,
        OutQuad,
        InOutQuint
    }
    
    public enum OtherEnum
    {
        Enum1
    }
    
    [Space(20), Header("Check with ENUM")]
    public EaseType easeType;
    
    [ShowWhen("easeType", EaseType.Linear)]
    public string stringWhenLinear = "Linear";
    
    [ShowWhen("easeType", new object[]{EaseType.Linear, EaseType.OutQuad})]
    public string stringWhenLinearAndOutQuad = "LinearAndOutQuad";
    
    [ShowWhen("easeType", EaseType.InOutQuint)]
    public string stringWhenInOutQuint = "InOutQuint";
    
    [ShowWhen("easeType")]
    public string stringErrorNeedParam;
    
    [ShowWhen("easeType",5)]
    public string stringErrorNotEnum;

    public OtherEnum otherEnum;
    
    [ShowWhen("otherEnum", new object[]{OtherEnum.Enum1, EaseType.Linear})]
    public string stringErrorWrongEnumType;

    #endregion

    #region Int Region

    [Space(20), Header("Check with INT")]
    public int intValue;
    
    [ShowWhen("intValue", ">5")]
    public string stringWhenGreaterThan5 = "Greater Than 5";
    
    [ShowWhen("intValue", ">3+5")]
    public string stringErrorNotKnownOperation;

    #endregion

    #region Float Region

    [Space(20), Header("Check with FLOAT")]
    public float floatValue;

    [ShowWhen("floatValue", "!=2")]
    public GameObject showWhenOtherThan2;
    
    [ShowWhen("floatValueError", ">5")]
    public string stringErrorParameterNotKnown;
    
    [ShowWhen("stringErrorParameterNotKnown", ">+5")]
    public string stringErrorTypeNotSupported;

    #endregion

}

also for some reason it dosnt work for arrays

Made a change to this so that it works in properties that aren't at the root level, solution for which was found here: https://www.brechtos.com/hiding-or-disabling-inspector-properties-using-propertydrawers-within-unity-5/

    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        ShowWhenAttribute attribute = (ShowWhenAttribute) this.attribute;
        var propPath = property.propertyPath;
        var conditionalPath = propPath.Replace(property.name, attribute.conditionFieldName);
        SerializedProperty conditionField = property.serializedObject.FindProperty(conditionalPath);