[英]Given a string as the type name of a generic class, how can I create the instance in runtime. If it is not possible, Is there another way?
[英]Eiffel: Is there a way to test a given Generic parameter of a Class without any attached instance of it?
有没有办法在没有任何附加实例的情况下测试类的给定泛型参数?
class BAG[G -> MOUSE]
feature --
discriminate
do
if G.conforms_to (MAMMAL) then
io.putstring ("you gave me a real animal")
elseif G.conforms_to (COMPUTER_ACCESSORY) then
io.putstring ("Seems you don't like animals such as computers")
else
io.pustring ("Still dont know what you are dealing with")
end
end
您几乎钉死了它。 缺少的部分是花括号和括号:
if ({G}).conforms_to ({MAMMAL}) then
io.put_string ("You gave me a real animal.")
elseif ({G}).conforms_to ({COMPUTER_ACCESSORY}) then
io.put_string ("Seems you don't like animals such as computers.")
else
io.put_string ("Still don't know what you are dealing with.")
end
说明:
{FOO}
(其中FOO
是类型名称)代表类型对象。 它适用于任何类型,包括形式泛型,例如{G}
和{MAMMAL}
。 {FOO}.bar
保留用于非对象调用。 但是这里我们要对类型对象进行对象调用。 因此, {G}
括在括号中: ({G}).conforms_to
{G}.conforms_to
(而不是{G}.conforms_to
)。
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