我怎样才能大写数组的每个元素？

Question

如何将元素数组转换为大写？预期的产出将是：

["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]  
=> ["MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY"]

以下不起作用并将其作为小写。

Day.weekday.map(&:name).each {|the_day| the_day.upcase }
 => ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"] 

Answer 1

返回一个新数组

如果要返回大写数组，请使用 #map ：

array = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]

# Return the uppercased version.
array.map(&:upcase)
=> ["MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY"]

# Return the original, unmodified array.
array
=> ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]

如您所见，原始数组未被修改，但您可以在任何可以使用表达式的地方使用#map的大写返回值。

到位更新数组

如果您想要在适当的位置大写数组，请改为使用 #map！：

array = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
array.map!(&:upcase)
array
=> ["MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY"]

Answer 2

这应该有效：

Day.weekday.map(&:name).map(&:upcase)

或者，如果你想节省一些CPU周期

Day.weekday.map{|wd| wd.name.upcase}

Answer 3

在您的示例中，将“each”替换为“map”。

虽然'each'遍历数组，但它不会创建包含块返回值的新数组。