Question

a = ["Select", "Choice", "Prime"]
a.each do |f|
    f.downcase = f.new
    f.grade = f
end

不是这样做的方法

select = Steak.new
select.grade = "Select"
choice = Steak.new
choice.grade = "Choice"
prime = Steak.new
prime.grade = "Prime"

是否有可能使用每个类实例化几个类似的类？

还是另一种方式？必须能够更有效地做到这一点。

Answer 1

当然可以：

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<i class="fa fa-check-circle-o"></i>

.fa {
    position: relative;
    z-index: 2;
    top: -35px;
    left: 50%;
}

Answer 2

好的，足够简单：

int

然而，它看起来真的是等级是牛排的重要特征。也许它应该像这样构造函数的一部分？

grades = ["Select", "Choice", "Prime"]
steaks = grades.map do |grade|
  steak = Steak.new
  steak.grade = grade.downcase
  steak
end

我认为创建一个初始化方法可以作为读者的练习。

Answer 3

如果你想为每个实例命名（所以使用哈希而不是数组），你可以这样做：

steaks = {}
["Select", "Choice", "Prime"].each do |grade|
    # I think using a symbol as key in this case is nicer
    steaks[grade.downcase.to_sym] = Steak.new(grade)
end

或者像你问的那样使用地图更短/最佳（支持从ruby-2.1开始）：

steaks = ["Select", "Choice", "Prime"].map{ |g| 
    [g.downcase.to_sym, new Steak(grade)] 
}.to_h

另一种选择是创建一个Butcher类，它抽象出所有这些。

butcher = new Butcher.new
butcher.addNewSteak(Steak.new("Select"))
butcher.addNewSteak(Steak.new("Choice"))
butcher.addNewSteak(Steak.new("Prime"))

# Or added/created using a loop
["Select", "Choice", "Prime"].each do |grade|
    butcher.addNewSteak(Steak.new(grade)
end   

# Get a list of steaks
butcher.getAllSteaks()

# Get steak by grade 
bucher.getSteakByGrade("Select")

# Get all steaks by grade greater than
bucher.getSteakGradeGT("Choice")

Butcher课程的实施被故意排除在外。详细说明是对Alejandro C答案提出的问题的回应。

Answer 4

做你要求的最简单的方法：

steaks = ["Select", "Choice", "Prime"].map do |grade|
  s = Steak.new
  s.grade = grade.downcase
  s
end

另一方面，我建议反对让grade成为可变成员。可变性导致错误。如果grade是Steak的基本部分，则应在构造函数中对其进行初始化：

class Steak
  def initialize(grade)
    @grade = grade.downcase
  end
end

然后你的代码会更简单

steaks = ["Select", "Choice", "Prime"].map do |grade|
  Steak.new grade
end

Answer 5

使用这种结构，你得到一个哈希，例如： :prime为关键字，Steak.new("Prime")为值。它可以更容易地迭代你的所有牛排，如果你想要一个特定的牛排，只需使用steaks[:prime]：

class Steak
  attr_reader :grade
  def initialize(grade)
    @grade = grade
  end

  def to_s
    format("Steak %s", grade)
  end
end

steaks = ["Select", "Choice", "Prime"].map{|grade| [grade.downcase.to_sym, Steak.new(grade)]}.to_h

p steaks
# {:select=>#<Steak:0x000000013e7000 @grade="Select">,
#  :choice=>#<Steak:0x000000013e6f60 @grade="Choice">,
#  :prime=>#<Steak:0x000000013e6ec0 @grade="Prime">}

puts steaks.values
# Steak Select
# Steak Choice
# Steak Prime

puts steaks[:select].grade # => "Select"

如果你真的想要牛排的3个独立变量：

select, choice, prime = ["Select", "Choice", "Prime"].map{|grade| Steak.new(grade)}

ruby使用每个实例化类

5 个答案: