Array allow child class types

1

Hello, I’m with a problem actually, I have a class CommandLineOption. And I made some others class inherit from CommandLineOption.

CommandLineOption have “option” as parameter, and this parameter is an array with others CommandLineOption items. But how can I allow this array to accept CommandLineOption class and their class are inherit them?

Normally, it’s this:
Array(ISM::CommandLineOption).new

But this Array allow only CommandLineOption, not classes inherit of it

2

Array(ISM::CommandLineOption) allows instances of that type and its children. I think you’re running into Inheritance - Crystal. But it’s hard to say without some examples/errors.

3

Hmmmm… yes normally, but it’s strange because I have this bug. It’s my problem actually:


~/Documents/Programmation/ISM ❯❯❯ crystal Main.cr software install                            ✘ 1 master ✖ ✱ ◼
Showing last frame. Use --error-trace for full trace.

In ISM/CommandLineOption.cr:17:13

 17 | @options = options
      ^-------
Error: instance variable '@options' of ISM::CommandLineOption must be Array(ISM::CommandLineOption), not Array(ISM::Option::SoftwareInstall)

But I’m sure what you said is true, because I have one other class do something similar, and I don’t have this problem.

4

Normally, I initialize the value of my child class with this:

[ ISM::Option::SoftwareInstall.new ]

But if I don’t do that:
[ ISM::Option::SoftwareInstall.new ] of ISM::CommandLineOption
It don’t work. But it’s not very clean (I think) like that.

5

This confirms my suspicion. Unfortunately this is best you can do at the moment. I’d checkout that link I posted for more details.

6

I think it’s not really proper, no ?

7

What isn’t proper? As stated in the link, [ ISM::Option::SoftwareInstall.new ] is a Array(ISM::Option::SoftwareInstall) even if that type inherits from ISM::CommandLineOption. If you want an array of child types to be typed as the parent class you need to use of ISM::CommandLineOption. That’s just how things work at the moment.

8

Ah okay. I wasn’t sure. Thanks you very much