Ruby bits


Outline
  1. 1. 目錄
  2. 2. 1. Unless 更直覺
    1. 2.1. 一行表達 if
  3. 3. 2. nil treated as false
  4. 4. 3. 給予初始值 - “OR”
  5. 5. 4. RETURN VALUES
  6. 6. 5. Symbol

目錄

  1. if、Unless
  2. nil
  3. 給予初始值
  4. RETURN VALUES
  5. symbol

1. Unless 更直覺

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# bad
if ! tweets.empty?
  puts "Timeline:"
  puts tweets
end

# good
unless tweets.empty?
  puts "Timeline:"
  puts tweets
end

一行表達 if

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puts pin_number == pin ? "Balance: $#{@balance}." : pin_error
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if pin_number == pin
  puts "Balance: $#{@balance}."
else
  puts pin_error
end

2. nil treated as false

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# bad
if attachment.file_path != nil
  attachment.post
end
# good
if attachment.file_path
  attachment.post
end

3. 給予初始值 - “OR”

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tweets = timeline.tweets || []
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result = nil || 1      # =>1
result =   1 || nil    # =>1
result =   1 || 2      # =>1
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result2 = nil || 1     # =>1
等價於
result2 ||= 1          # =>1

但是 if else 比較易讀

4. RETURN VALUES

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# bad
def list_url(user_name, list_name)
  if list_name
    url = "https://twitter.com/#{user_name}/#{list_name}" 
  else
    url = "https://twitter.com/#{user_name}" 
  end
  url
end
# good
def list_url(user_name, list_name)
  if list_name
    "https://twitter.com/#{user_name}/#{list_name}"
  else
    "https://twitter.com/#{user_name}"
  end 
end

5. Symbol

string 與 symbol 轉換

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"a".to_sym
=> :a
"a".intern
=> :a
:a.to_s
=> "a"
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:hello.is_a? Symbol
=> true
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