Conditonaly hide some field in Unity inspector, base on other field's value (from http://www.brechtos.com/hiding-or-disabling-inspector-properties-using-propertydrawers-within-unity-5/)

ConditionalHideAttribute.cs

using UnityEngine;
using System;

//Original version of the ConditionalHideAttribute created by Brecht Lecluyse (www.brechtos.com)
//Modified by: -

[ AttributeUsage( AttributeTargets.Field ) ]
public class ConditionalHideAttribute : PropertyAttribute
{
    public readonly string ConditionalSourceField;
    public string ConditionalSourceField2 = "";
    public bool HideInInspector = false;
    public bool Inverse = false;

    // Use this for initialization
    public ConditionalHideAttribute( string conditionalSourceField )
    {
        ConditionalSourceField = conditionalSourceField;
    }
}

ConditionalHidePropertyDrawer.cs

using UnityEngine;
using UnityEditor;

//Original version of the ConditionalHideAttribute created by Brecht Lecluyse (www.brechtos.com)
//Modified by: -

[ CustomPropertyDrawer( typeof( ConditionalHideAttribute ) ) ]
public class ConditionalHidePropertyDrawer : PropertyDrawer
{
    public override void OnGUI( Rect position, SerializedProperty property, GUIContent label )
    {
        var condHAtt = (ConditionalHideAttribute) attribute;
        var enabled = GetConditionalHideAttributeResult( condHAtt, property );

        var wasEnabled = GUI.enabled;
        GUI.enabled = enabled;
        if ( !condHAtt.HideInInspector || enabled )
        {
            EditorGUI.PropertyField( position, property, label, true );
        }

        GUI.enabled = wasEnabled;
    }

    public override float GetPropertyHeight( SerializedProperty property, GUIContent label )
    {
        var condHAtt = (ConditionalHideAttribute) attribute;
        var enabled = GetConditionalHideAttributeResult( condHAtt, property );

        if ( !condHAtt.HideInInspector || enabled )
        {
            return EditorGUI.GetPropertyHeight( property, label );
        }
        else
        {
            //The property is not being drawn
            //We want to undo the spacing added before and after the property
            return -EditorGUIUtility.standardVerticalSpacing;
        }
    }

    private bool GetConditionalHideAttributeResult( ConditionalHideAttribute condHAtt, SerializedProperty property )
    {
        var enabled = true;

        var propertyPath =
            property.propertyPath; //returns the property path of the property we want to apply the attribute to
        string conditionPath;

        if ( !string.IsNullOrEmpty( condHAtt.ConditionalSourceField ) )
        {
            //Get the full relative property path of the sourcefield so we can have nested hiding
            conditionPath =
                propertyPath.Replace( property.name,
                    condHAtt.ConditionalSourceField ); //changes the path to the conditionalsource property path
            var sourcePropertyValue = property.serializedObject.FindProperty( conditionPath );
            
            if ( sourcePropertyValue != null )
            {
                enabled = CheckPropertyType( sourcePropertyValue );
            }
            else
            {
                //Debug.LogWarning("Attempting to use a ConditionalHideAttribute but no matching SourcePropertyValue found in object: " + condHAtt.ConditionalSourceField);
            }
        }

        if ( !string.IsNullOrEmpty( condHAtt.ConditionalSourceField2 ) )
        {
            conditionPath =
                propertyPath.Replace( property.name,
                    condHAtt.ConditionalSourceField2 ); //changes the path to the conditionalsource property path
            var sourcePropertyValue2 = property.serializedObject.FindProperty( conditionPath );
            
            if ( sourcePropertyValue2 != null )
            {
                enabled = enabled && CheckPropertyType( sourcePropertyValue2 );
            }
            else
            {
                //Debug.LogWarning("Attempting to use a ConditionalHideAttribute but no matching SourcePropertyValue found in object: " + condHAtt.ConditionalSourceField);
            }
        }

        if ( condHAtt.Inverse ) enabled = !enabled;

        return enabled;
    }

    private bool CheckPropertyType( SerializedProperty sourcePropertyValue )
    {
        switch ( sourcePropertyValue.propertyType )
        {
            case SerializedPropertyType.Boolean:
                return sourcePropertyValue.boolValue;
            case SerializedPropertyType.ObjectReference:
                return sourcePropertyValue.objectReferenceValue != null;
            default:
                Debug.LogError( "Data type of the property used for conditional hiding [" +
                                sourcePropertyValue.propertyType + "] is currently not supported" );
                return true;
        }
    }
}