问题描述
在父子关系中具有cloudformation模板的集合，并希望将AWS :: IAM :: Role传递到子堆栈的参数中，并使用GetAttr获取Arn。
Have a collection of cloudformation templates in a parent-child relationship and want to pass an AWS::IAM::Role into the parameters of a child stack and use GetAttr to get the Arn.
这将使验证失败，因为只能对资源而不是参数调用GetAttr。
This fails validation because can only call GetAttr on resources, not on parameters.
任何人都知道/猜测为什么以此方式设计？
Anyone know/guess why this is designed in this way?
这不是问题，因为可以通过将Arn传递到堆栈中来解决，我很好奇
It's not a problem as it can be worked around by just passing the Arn into the stack, I'm just curious really
推荐答案
什么 Fn :: GetAttr 和 Parameters 正在尝试在 AWS CloudFormation 中执行的操作根本不同。根据AWS文档：
What Fn::GetAttr and Parameters are trying to do in AWS CloudFormation is fundamentally different. As per AWS docs:
[1]
[2]
我相信您的困惑源于您试图从以下方面考虑这一事实：面向对象/其他编程范例，其中资源和参数是某种对象，而 Fn :: GetAttr 是一个泛型函数，用于检索作为参数传入的引用的值。
I believe your confusion is stemming from the fact that you're trying to think of this in terms of the object-oriented/some other programming paradigm, where Resources and Parameters are some kind of objects and Fn::GetAttr is a generic function which retrieves the value of a reference that's passed in as an argument.
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