排序属性和随机复发

Question

由于场地有一个字段“featured_level”，可以从0到N.

我需要返回由featured_level，下令但具有相同的随机场馆的秩序场馆featured_level。

UPDATE：

使用给出答案，我有这样的方法：

def self.by_featured_level 
    all.group_by {|v| v.featured_level}.inject([]) { |memo, (level,values)| 
    memo << { level => values.shuffle } 
    }.map { |hash| hash.values }.flatten.reverse 
end 

但它没有下面的测试（也没有实数的正常工作），我还在努力算起来，使用的测试：

describe "by featured level" do 
    before do 

    @venue1 = create(:venue, featured_level: 5) 
    @venue2 = create(:venue, featured_level: 2) 
    @venue3 = create(:venue, featured_level: 4) 
    @venue4 = create(:venue, featured_level: 2) 
    @venue5 = create(:venue, featured_level: 0) 
    @venue6 = create(:venue, featured_level: 2) 
    @venues = Venue.by_featured_level 

    end 

    it { 
    start_with_hightest = @venues.index(@venue1) == 0 
    expect(start_with_hightest).to be_truthy 
    } 
    it { 
    second_hightest_is_2nd = @venues.index(@venue3) == 1 
    expect(second_hightest_is_2nd).to be_truthy 
    } 
    it { 
    ends_with_lowest = @venues.last.id == @venue5.id 
    expect(ends_with_lowest).to be_truthy 
    } 
end 

Answer 1

我原本需要一个ActiveRecord ::关系，而不是一个数组（这是由@ zezetic的回答回报，所以最后我做：

scope :by_featured_level, -> { 
     select("venues.*, (random() * 9 + 1) AS rdn").order('featured_level DESC, rdn') } 

Answer 2

让我们开始收集场馆：

require 'ostruct' 

@venue1 = OpenStruct.new(id: :a, level: 0) 
@venue2 = OpenStruct.new(id: :b, level: 2) 
@venue3 = OpenStruct.new(id: :c, level: 2) 
@venue4 = OpenStruct.new(id: :d, level: 2) 
@venue5 = OpenStruct.new(id: :e, level: 4) 
@venue6 = OpenStruct.new(id: :f, level: 5) 

@venues = [@venue1, @venue2, @venue3, @venue4, @venue5, @venue6] 

我们希望每级随机化，所以我们将创建组：

@venues.group_by { |v| v.level } 

这将返回一个散列结果，其中场地由每个级别索引。

我们遍历散列，并返回一个新的哈希其中的值已经随机：

@venues. 
    group_by {|v| v.level}. 
    inject([]) { |memo, (level,values)| 
    memo << { level => values.shuffle } 
    } 

该散列现在可以变平，因此最终的结果是散列的名单，每级随机：

@venues. 
    group_by {|v| v.level}. 
    inject([]) { |memo, (level,values)| 
    memo << { level => values.shuffle } 
    }. 
    map { |hash| hash.values }. 
    flatten