ruby-on-rails - ruby rails : How to group list of names based on the initial?

Question

我有一个数组中的名称列表，例如:

['John', 'Smith', 'Doe', 'Lee', 'Jack']

我希望它像这样分组:

['Doe']
['Jack', 'John']
['Lee']
['Smith']

我如何使用 ruby​​ on rails 做到这一点？

Answer 1

可枚举的 group_by是你的 friend :

names = ['John', 'Smith', 'Doe', 'Lee', 'Jack']
names.group_by{ |n| n[0] } 
# => {"J"=>["John", "Jack"], "S"=>["Smith"], "D"=>["Doe"], "L"=>["Lee"]}
names.group_by{ |n| n[0] }.values 
# => [["John", "Jack"], ["Smith"], ["Doe"], ["Lee"]]

来自文档:

Groups the collection by result of the block. Returns a hash where the keys are the evaluated result from the block and the values are arrays of elements in the collection that correspond to the key.

如果您想按字母顺序排列它们，只需在使用 group_by 之前对初始数组进行排序。因为 Ruby 维护哈希的插入顺序，所以哈希的结果值也将按顺序排列:

names.sort.group_by{ |n| n[0] }.values 
# => [["Doe"], ["Jack", "John"], ["Lee"], ["Smith"]]