design-by-contract - 埃菲尔：附加检查到要求语句中的未知标识符

Question

    require
        valid_item: attached item as l_i and then l_i.valid_for_insert or l_i.valid_for_update

为什么我这里有一个未知的标识符和 l_i??!!!

Answer 1

尝试

valid_item: attached item as l_i and then (l_i.valid_for_insert or l_i.valid_for_update)

注意你也可以这样做

item_set: attached item as l_i 
valid_item: l_i.valid_for_insert or l_i.valid_for_update

您可以重用l_i先前前提条件中的对象测试局部变量。