Ruby - 用另一个字符串替换第一次出现的子字符串

Question

a = "foobarfoobarhmm"

我希望输出为"fooBARfoobarhmm"

即只有第一次出现的"bar"应该用"BAR"代替.

Answer 1

用途#sub:

a.sub('bar', "BAR")

Answer 2

String#sub就像Yossi已经说过的那样,你就是你所需要的.但我会使用Regexp,因为它更快:

a = 'foobarfoobarhmm'
output = a.sub(/foo/, 'BAR')

Answer 3

要替换第一个匹配项,只需执行以下操作:

str = "Hello World"
str['Hello'] = 'Goodbye'
# the result is 'Goodbye World'

你甚至可以使用正则表达式:

str = "I have 20 dollars"
str[/\d+/] = 500.to_s
# will give 'I have 500 dollars'