where T:new() 是什么意思
经常看到方法后面加where T:new() ,下面来解释下
比如如下这个方法
protected
static
T CreateNewInstance<T>() where T :
new
()
{
return
new
T();
}
解释如下:
T后面跟的是泛型约束,啥叫泛型约束,就是你必须要符合这个规则来,不然就不让你编译通过 。
后面的new()代表这个T 必须有一个无参的构造函数,
当然一个新建的class。这个类做为T,也是可以编译通过的。
因为如果类中没有构造函数会默认就加一个无参的构造函数,刚好符合这个约束。
比如
Public Class People{}
这个people 做为T默认是可以编译通过的。因为他等同于
Public Class People(public People(){})
但如果有一个这样的People就会编译不通过了。
Public Class People(public People(string s){}})
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