用于遍历哈希数组的ruby代码的说明

Question

我有两个脚本，它们的行为各不相同，一次运行两次，另两次运行两次，无法理解为什么任何一个plz都能帮助您？

脚本-1

@newArray=[{grade_id:"1",sections:"4"},
           {grade_id:"2",sections:"8"},
           {grade_id:"3",sections:"7"},
           {grade_id:"4",sections:"7"},
           {grade_id:"5",sections:"3"},
           {grade_id:"6",sections:"3"},
           {grade_id:"7",sections:"3"}]

@total_grades_passed = @newArray.count
@grades_counter = 0

while @grades_counter < @total_grades_passed do
  @newArray[@grades_counter].each do |key, value|
     print [key]
     puts [value] 
  end
  @grades_counter += 1
end

给出以下输出。

[:grade_id]1
[:sections]4
[:grade_id]2
[:sections]8
[:grade_id]3
[:sections]7
[:grade_id]4
[:sections]7
[:grade_id]5
[:sections]3
[:grade_id]6
[:sections]3
[:grade_id]7
[:sections]3

而SCRIPT-2则提供完全不同的输出。

@newArray=[{grade_id:"1",sections:"4"},
           {grade_id:"2",sections:"8"},
           {grade_id:"3",sections:"7"},
           {grade_id:"4",sections:"7"},
           {grade_id:"5",sections:"3"},
           {grade_id:"6",sections:"3"},
           {grade_id:"7",sections:"3"}]

@total_grades_passed = @newArray.count
@grades_counter = 0  

while @grades_counter < @total_grades_passed do
  @newArray[@grades_counter].each do |x,y|
    @grade_id = @newArray[@grades_counter][:grade_id].to_i
    @no_of_sections = @newArray[@grades_counter][:sections].to_i
    puts "Grade id is #{@grade_id} and its class is #{@grade_id.class}"
    puts "section is #{@no_of_sections} and its class is #{@no_of_sections.class}"
  end
  @grades_counter += 1
end

提供以下奇怪的输出。

Grade id is 1 and its class is Fixnum
section is 4 and its class is Fixnum
Grade id is 1 and its class is Fixnum
section is 4 and its class is Fixnum
Grade id is 2 and its class is Fixnum
section is 8 and its class is Fixnum
Grade id is 2 and its class is Fixnum
section is 8 and its class is Fixnum
Grade id is 3 and its class is Fixnum
section is 7 and its class is Fixnum
Grade id is 3 and its class is Fixnum
section is 7 and its class is Fixnum
Grade id is 4 and its class is Fixnum
section is 7 and its class is Fixnum
Grade id is 4 and its class is Fixnum
section is 7 and its class is Fixnum
Grade id is 5 and its class is Fixnum
section is 3 and its class is Fixnum
Grade id is 5 and its class is Fixnum
section is 3 and its class is Fixnum
Grade id is 6 and its class is Fixnum
section is 3 and its class is Fixnum
Grade id is 6 and its class is Fixnum
section is 3 and its class is Fixnum
Grade id is 7 and its class is Fixnum
section is 3 and its class is Fixnum
Grade id is 7 and its class is Fixnum
section is 3 and its class is Fixnum

谁能解释一下为什么会这样，两个脚本及其后续输出之间的区别是由于哪几行代码引起的？ 我只想提取grade_id和section_id并进行一些计算，然后移至下一对成绩和科目ID，并对它们进行相同的计算。

Answer 1

有更好，更清洁，更“红褐色”的方式来执行此操作。

如果grade_id和sections是您想要的，则可以这样访问：

@newArray.each do |hash|
  hash.each do |grade_id, sections|
    # do something
  end
end

还请注意，当您遍历哈希时，哈希将传递与密钥相同的次数。 这就是为什么您的文本输出两次的原因。

Answer 2

@newArray[@grades_counter].each内部的块代码将运行2次，因为每个哈希都有2对键值。

以及较短的代码版本：

@newArray.each do |hash|
  hash.each do |key, value|
    print [key]
    puts [value]
  end
end

Answer 3

在第二个示例中，您不想遍历哈希。 您正在遍历哈希键（即使您不使用它）。

您应该这样做：

@newArray=[{grade_id:"1",sections:"4"},{grade_id:"2",sections:"8"},
            {grade_id:"3",sections:"7"},{grade_id:"4",sections:"7"},
            {grade_id:"5",sections:"3"},{grade_id:"6",sections:"3"},
            {grade_id:"7",sections:"3"}]

@total_grades_passed = @newArray.count
@grades_counter = 0  

while @grades_counter < @total_grades_passed do

    @grade_id = @newArray[@grades_counter][:grade_id].to_i
    @no_of_sections = @newArray[@grades_counter][:sections].to_i
    puts "Grade id is #{@grade_id} and its class is #{@grade_id.class}"
    puts "section is #{@no_of_sections} and its class is #{@no_of_sections.class}"

  @grades_counter += 1
end