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来源：雅诚德英语网
In this case we get a component we know we have, then cast it to a specific type and conditionally do something.
就是根据已有的组件转换成另一种类型来有条件的处理一些事情。
In this case we get a component we know we have, then cast it to a specific type and conditionally do something.
就是根据已有的组件转换成另一种类型来有条件的处理一些事情。