数字填充作为字符串消息的一部分

Question

我希望有一个类似"The time is #{hours}:#{minutes}"的字符串，以便hours和minutes始终为零填充（2位数）。我该怎么办？

Answer 1

见ljust，rjust and center here。

示例是：

"3".rjust(2, "0") => "03"

Answer 2

您可以使用时间格式：Time#strftime

t1 = Time.now
t2 = Time.new(2012, 12, 12)
t1.strftime "The time is %H:%M" # => "The time is 16:18"
t2.strftime "The time is %H:%M" # => "The time is 00:00"

或者，您可以使用'%' format operator

来使用字符串格式

t1 = Time.now
t2 = Time.new(2012, 12, 12)
"The time is %02d:%02d" % [t1.hour, t1.min] # => "The time is 16:18"
"The time is %02d:%02d" % [t2.hour, t2.min] # => "The time is 00:00"

Answer 3

对字符串使用格式运算符：%运算符

str = "The time is %02d:%02d" %  [ hours, minutes ]

Reference

格式字符串与C函数printf中的相同。

Answer 4

或类似的东西：

1.9.3-p194 :003 > "The time is %02d:%02d" % [4, 23]
 => "The time is 04:23" 

Answer 5

sprintf一般很有用。

1.9.2-p320 :087 > hour = 1
 => 1 
1.9.2-p320 :088 > min = 2
 => 2 
1.9.2-p320 :092 > "The time is #{sprintf("%02d:%02d", hour, min)}"
 => "The time is 01:02" 
1.9.2-p320 :093 > 

1.9.2-p320 :093 > str1 = 'abc'
1.9.2-p320 :094 > str2 = 'abcdef'
1.9.2-p320 :100 > [str1, str2].each {|e| puts "right align #{sprintf("%6s", e)}"}
right align    abc
right align abcdef