ruby 如何将数组的每个元素大写？
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How can I uppercase each element of an array?
提问by Michael Durrant
How can I turn an array of elements into uppercase? Expected output would be:
如何将元素数组转换为大写？预期输出将是：
["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
=> ["MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY"]
The following didn't work and left them as lower case.
以下不起作用并将它们保留为小写。
Day.weekday.map(&:name).each {|the_day| the_day.upcase }
=> ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
回答by Todd A. Jacobs
Return a New Array
返回一个新数组
If you want to return an uppercased array, use #map:
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"]
As you can see, the original array is not modified, but you can use the uppercased return value from #map anywhere you can use an expression.
如您所见，原始数组没有被修改，但是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。
Update Array in Place
就地更新数组
If you want to uppercase the array in-place, use #map!instead:
如果要就地大写数组，请使用#map! 反而：
array = ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]
array.map!(&:upcase)
array
=> ["MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY"]
回答by Sergio Tulentsev
This should work:
这应该有效：
Day.weekday.map(&:name).map(&:upcase)
Or, if you want to save some CPU cycles
或者，如果您想节省一些 CPU 周期
Day.weekday.map{|wd| wd.name.upcase}
回答by christianblais
In your example, replace 'each' with 'map'.
在您的示例中，将“每个”替换为“地图”。
While 'each' iterates through your array, it doesn't create a new array containing the values returned by the block.
虽然 'each' 遍历数组，但它不会创建包含块返回值的新数组。
