Unity 中常见错误之一UnassignedReferenceException: The variable button of CityScript has not been assigned.

UnassignedReferenceException: The variable button of CityScript has not been assigned.这是因为我自己挂了两个CityScript脚本在不同的组件上面导致出现了这个问题。所以有出现这个问题的童鞋，找找看看有没有挂两个一样的脚本。