如何在Eiffel中初始化对象数组? [英] How to initialise an array of objects in Eiffel?

问题描述

我正在尝试使用Eiffel实现生产者－消费者问题的解决方案.我有一个类PRODUCER的数组p和一个类CONSUMER的数组c声明并初始化如下:

I am trying to implement a solution to the Producer-Consumer problem using Eiffel. I have an array p of class PRODUCER and an array c of class CONSUMER declared and initialized as following:

    local
        p:attached ARRAY[PRODUCER]
        c:attached ARRAY[CONSUMER]
    do
        !!p.make(1,5)
        !!c.make(1,5)

但是，当我尝试访问数组组件之一中的功能(例如p.at(i).somefeature())时，它给出了运行时异常，提示对虚空目标进行功能调用".

But when I try to access a feature in one of the components of the array (like p.at(i).somefeature()), it gives a runtime exception saying "Feature call on void target".

关于如何解决此问题的任何想法?是因为我没有为数组的各个组件调用创建过程吗?还是创建数组的方法存在基本缺陷?谢谢.

Any ideas on how to solve this? Is it because I am not calling a creation procedure for individual components of the array? Or is there a basic flaw in the approach to create the arrays? Thanks.

我认为出现此问题是因为作为引用类型的数组的各个组件(在这种情况下，是生产者或消费者)被初始化为void.建议的解决方案是使用make_filled(default_value:T; low，high:INTEGER;)，其中T是复杂类型.字符串数组的示例为 string_list:ARRAY [STRING] string_list.make_filled("，low，high) 导致将string_list的每个元素初始化为一个空格的字符串.关于如何为类PRODUCER赋予默认值的任何帮助吗?谢谢

I figured the problem occurs because the individual components of the arrays (in this case, a producer or a consumer), being a reference type is initialized to void. The solution suggested is to use make_filled(default_value:T;low,high:INTEGER;), where T is the complex type. An example is given for string arrays as string_list:ARRAY[STRING] string_list.make_filled(" ",low,high) causing each element of string_list to be initialized to a string that is a blank space. Any help on how to give a default value for the class PRODUCER? Thanks

我想我已经找到解决问题的办法.我只需要创建PRODUCER和CONSUMER的实例，并在make_filled的默认值中使用它们.然后我可以操纵p [i]和c [i].

I think I figured out the solution to the problem. I just had to create an instance of PRODUCER and CONSUMER and use those in the default value in make_filled. Then I can manipulate p[i] and c[i].

这不是一种超级有效的方法，因此，如果有更好的解决方案，请务必共享.谢谢.

This is nota super efficient way, so if there is a better solution, please do share it. Thanks.

推荐答案

{ARRAY}.make_filled.如果元素不同，则可以将数组一一填充:

{ARRAY}.make_filled is normally used when all the elements of the array should be the same. If the elements are different, the array can be filled one by one:

create p.make_empty
p.force (create {PRODUCER}.make ("producer 1"), 1) -- Use appropriate code to
p.force (create {PRODUCER}.make ("producer 2"), 2) -- create PRODUCER objects.
...

创建数组还有一种过时的语法，因此必须谨慎使用:

There is also a somewhat obsolete syntax to create arrays, so it has to be used with care:

p := <<
    create {PRODUCER}.make ("producer 1"), -- Or some other code
    create {PRODUCER}.make ("producer 2")  -- to create producers.
>>

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