英文:
Rspec how to determine if a let block has been defined?
问题
在Rspec中，我想要利用super()来调用一个已定义的let块（如果存在的话），或者在不存在时设置一个新的值，我想在一个shared_example组内使用这个功能，但我找不到如何实现这个目标。
我尝试过检查@some_let是否存在，尝试过检查some_let的超级方法是否由kernel拥有，但都没有提供有用的信息；我无法访问instance_methods或instance_method，因为Rspec不允许我这样做，而在互联网上搜索方法也没有找到答案。
我希望能够像这样做：
shared_examples 'a shared example' do
let(:some_let) { let_exists?(:some_let) ? super() : some_new_value }
end
是否有类似let_exists?的方法或类似的方法？
英文:
In Rspec, I want to take advantage of using super() to call a defined let block if it exists or set a new value if it hasn't, I want to use this within a shared_example group but I just can't find how to do this.
I've tried checking if @some_let exists, I've tried checking if a super method of :some_let is owned by the kernel or not and none of them provide anything useful; I can't access instance_methods or instance_method because Rspec won't let me and searching the internet for a method hasn't revealed an answer.
I want to be able to do something like this:
shared_examples 'a shared example' do
let(:some_let) { let_exists?(:some_let) ? super() : some_new_value }
end
is there a method like let_exists? or something to that effect?
答案1
得分: 7
假设在包含共享示例之前调用了 let，则以下内容将起作用：
shared_examples 'a shared example' do
let(:some) { 'fallback value' } unless method_defined?(:some)
end
describe 'with let' do
let(:some) { 'explicit value' }
include_examples 'a shared example'
it { expect(some).to eq('explicit value') }
end
describe 'without let' do
include_examples 'a shared example'
it { expect(some).to eq('fallback value') }
end
method_defined? 检查当前上下文中是否已经定义了名为 some 的方法。如果没有定义，则定义该方法以提供默认值。
另一种（通常更简单的）方法是始终定义一个默认值，并在包含共享示例后提供显式值（从而覆盖默认值）：
shared_examples 'a shared example' do
let(:some) { 'default value' }
end
describe 'with let' do
include_examples 'a shared example' # <- 顺序很重要
let(:some) { 'explicit value' } # important
it { expect(some).to eq('explicit value') }
end
describe 'without let' do
include_examples 'a shared example'
it { expect(some).to eq('default value') }
end
英文:
Assuming that you call let before including the shared examples, this would work:
shared_examples 'a shared example' do
let(:some) { 'fallback value' } unless method_defined?(:some)
end
describe 'with let' do
let(:some) { 'explicit value' }
include_examples 'a shared example'
it { expect(some).to eq('explicit value') }
end
describe 'without let' do
include_examples 'a shared example'
it { expect(some).to eq('fallback value') }
end
method_defined? checks if a method called some has already been defined in the current context. If not, the method is defined to provide a default value.
Another (usually easier) approach is to always define a default value and to provide the explicit value after including the shared examples: (thus overwriting the default value)
shared_examples 'a shared example' do
let(:some) { 'default value' }
end
describe 'with let' do
include_examples 'a shared example' # <- order is
let(:some) { 'explicit value' } # important
it { expect(some).to eq('explicit value') }
end
describe 'without let' do
include_examples 'a shared example'
it { expect(some).to eq('default value') }
end
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