nil?
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provided by ruby
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可以使用在任何型別上
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只有nil才會return true, 否則return false
# 只有nil才會回傳true
nil.nil? => true
[].nil? => false
{}.nil? => false
0.nil? => false
false.nil? => false
"".nil? => false
" ".nil? => false
empty?
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provided by ruby
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僅用於 Hash、Array、Set、String
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當沒有任何元素時才會return true, 否則return false
當你將empty? 使用在沒有該方法的類別上, 會得到NoMethodError的exception, 所以你會需要使用檢查來避免程式在運行上不會崩潰
[].empty? => true
{}.empty? => true
Set.new.empty? => true
# 當用於string時, 可把他想像成bytes/characters的集合
"".empty? => true
" ".empty? => false
blank?
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provided by rails(in ActiveSupport)
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可以使用在任何型別上
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任何false相關的情況都會回傳true, (如nil and false)
如同你所看到的, blank? 比 empty? 更好用, 可以避免無法使用的資料處理上, 會回傳NoMethodErrors 錯誤
[].blank? => true
{}.blank? => true
Set.new.blank? => true
"".blank? => true
" ".blank? => true
false.blank? => true
nil.blank? => true
# 如果是Hash、Array、Set, 原理跟empty一樣, 如果沒有元素就回傳true
[nil].blank? => false
["", ""].blank? => false
{name: 'jasper'}.blank? => false
true.blank? => false
present?
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provided by rails
-
跟
blank?相反
true.present? => true
{name: 'jasper'}.present? => true
3.present? => true
false.present? => false
{}.present? => false
"".present? => false
" ".presnet? => false
[].present? => false
nil.present? => false
