Unity3D Handles by Propertydrawer

PositionHandleEditor.cs

#if UNITY_EDITOR
namespace Editor {
    using UnityEditor;

    [CustomEditor(typeof(MonoBehaviour), true, isFallback = true)]
    public class PositionHandleEditor : UnityEditor.Editor {
        
        void OnSceneGUI() {
            var t = target as MonoBehaviour;
            if(t == null) return;

            foreach(var fieldInfo in t.GetType().GetFields()) {
                try {
                    var attribs = fieldInfo.GetCustomAttributes(typeof(PositionHandleAttribute), false);
                    if(attribs.Length > 0 && fieldInfo.FieldType == typeof(Vector3)) {
                        Vector3 v = (Vector3) fieldInfo.GetValue(t);
                        v = Handles.PositionHandle((Vector3)v, Quaternion.identity);
                        Handles.Label(v, fieldInfo.Name);
                        fieldInfo.SetValue(t, v);
                    }
                }catch(System.Exception) {
                    // ignored
                }
            }

        }
    }

}
#endif
public class PositionHandleAttribute : PropertyAttribute {}

/// ------------

public class DummyClass : MonoBehaviour{
   [PositionHandle] public Vector3 TargetPosition;
}