Ruby-on-rails Rails 将散列数组映射到单个散列
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Rails mapping array of hashes onto single hash
提问by Bart Platak
I have an array of hashes like so:
我有一个像这样的哈希数组：
[{"testPARAM1"=>"testVAL1"}, {"testPARAM2"=>"testVAL2"}]
And I'm trying to map this onto single hash like this:
我正在尝试将其映射到这样的单个哈希上：
{"testPARAM2"=>"testVAL2", "testPARAM1"=>"testVAL1"}
I have achieved it using
我已经使用
par={}
mitem["params"].each { |h| h.each {|k,v| par[k]=v} }
But I was wondering if it's possible to do this in a more idiomatic way (preferably without using a local variable).
但我想知道是否有可能以更惯用的方式来做到这一点（最好不使用局部变量）。
How can I do this?
我怎样才能做到这一点？
回答by cjhveal
You could compose Enumerable#reduceand Hash#mergeto accomplish what you want.
你可以创作Enumerable#reduce并Hash#merge完成你想要的。
input = [{"testPARAM1"=>"testVAL1"}, {"testPARAM2"=>"testVAL2"}]
input.reduce({}, :merge)
is {"testPARAM2"=>"testVAL2", "testPARAM1"=>"testVAL1"}
Reducing an array sort of like sticking a method call between each element of it.
减少数组有点像在它的每个元素之间粘贴一个方法调用。
For example [1, 2, 3].reduce(0, :+)is like saying 0 + 1 + 2 + 3and gives 6.
例如[1, 2, 3].reduce(0, :+)就像说0 + 1 + 2 + 3和给6。
In our case we do something similar, but with the merge function, which merges two hashes.
在我们的例子中，我们做了一些类似的事情，但使用了合并函数，它合并了两个散列。
[{:a => 1}, {:b => 2}, {:c => 3}].reduce({}, :merge)
is {}.merge({:a => 1}.merge({:b => 2}.merge({:c => 3})))
is {:a => 1, :b => 2, :c => 3}
回答by shigeya
How about:
怎么样：
h = [{"testPARAM1"=>"testVAL1"}, {"testPARAM2"=>"testVAL2"}]
r = h.inject(:merge)
回答by Joshua Cheek
回答by Nikhil Mohadikar
Here you can use either injector reducefrom Enumerableclass as both of them are aliases of each other so there is no performance benefit to either.
在这里，您可以使用Enumerable类中的注入或减少，因为它们都是彼此的别名，因此两者都没有性能优势。
sample = [{"testPARAM1"=>"testVAL1"}, {"testPARAM2"=>"testVAL2"}]
result1 = sample.reduce(:merge)
# {"testPARAM1"=>"testVAL1", "testPARAM2"=>"testVAL2"}
result2 = sample.inject(:merge)
# {"testPARAM1"=>"testVAL1", "testPARAM2"=>"testVAL2"}
