问题:
你有一个泛型类包含一个由类自身定义类型参数的变量。由于对泛型对象的约束,你希望这个变量被初始化为其默认值。
解决方法:
非常简单的方法:只要使用default关键字初始化其值为默认值即可:
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使用这个类的代码可以参考这里:
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当初始化一个相同类型参数的变量时,你不能只是设置这些变量为null。如果这个变量是值类型,比如说int或char,那会是什么呢?那将不能运行,因为值类型不能是null的。你也许会想到一个nullable类型,比如long?或者Nullable<long>,可以被设为空。然而,编译器无法知道用户将使用什么类型参数去构造这个类型。
default关键字允许你告诉编译器在编译时,这个类型的默认值将被使用。如果提供的类型参数是数值(int,long,decimal),那么默认值将会是0。如果是引用类型,那么默认值将会是null。如果是结构体,那么这个结构体的默认值将根据其每一个字段的类型设为0或null。