用於遍歷哈希數組的ruby代碼的說明

Question

我有兩個腳本，它們的行為各不相同，一次運行兩次，另兩次運行兩次，無法理解為什么任何一個plz都能幫助您？

腳本-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

給出以下輸出。

[: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則提供完全不同的輸出。

@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

提供以下奇怪的輸出。

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

誰能解釋一下為什么會這樣，兩個腳本及其后續輸出之間的區別是由於哪幾行代碼引起的？ 我只想提取grade_id和section_id並進行一些計算，然后移至下一對成績和科目ID，並對它們進行相同的計算。

Answer 1

有更好，更清潔，更“紅褐色”的方式來執行此操作。

如果grade_id和sections是您想要的，則可以這樣訪問：

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

還請注意，當您遍歷哈希時，哈希將傳遞與密鑰相同的次數。 這就是為什么您的文本輸出兩次的原因。

Answer 2

@newArray[@grades_counter].each內部的塊代碼將運行2次，因為每個哈希都有2對鍵值。

以及較短的代碼版本：

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

Answer 3

在第二個示例中，您不想遍歷哈希。 您正在遍歷哈希鍵（即使您不使用它）。

您應該這樣做：

@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