Ruby -如何从字符串中选择一些字符
Ruby -如何从字符串中选择一些字符
提问于 2011-06-21 18:41:32
我正在尝试寻找一个函数来选择字符串的前100个字符。在PHP中，存在substr function
Ruby有类似的功能吗？
回答 2
Stack Overflow用户
回答已采纳
发布于 2011-06-21 18:43:26
尝试foo[0...100]，任何范围都可以。范围也可以变为负数。它是Ruby的well explained in the documentation。
Stack Overflow用户
发布于 2016-01-24 17:46:57
使用[]-operator (docs)：
foo[0, 100] # Get 100 characters starting at position 0
foo[0..99] # Get all characters in index range 0 to 99 (inclusive!)
foo[0...100] # Get all characters in index range 0 to 100 (exclusive!)Update for Ruby 2.7：Beginless ranges现在在这里(截至2019-12-25)，可能是“返回数组的第一个xx”的标准答案：
foo[...100] # Get all chars from the beginning up until the 100th (exclusive)使用.slice方法(docs)：
foo.slice(0, 100) # Get 100 characters starting at position 0
foo.slice(0...100) # Behaves the same as operator [] 为了完整性：
foo[0] # Returns the indexed character, the first in this case
foo[-100, 100] # Get 100 characters starting at position -100
# Negative indices are counted from the end of the string/array
# Caution: Negative indices are 1-based, the last element is -1
foo[-100..-1] # Get the last 100 characters in order
foo[-1..-100] # Get the last 100 characters in reverse order
foo[-100...foo.length] # No index for one beyond last characterUpdate for Ruby 2.6：Endless ranges现在就在这里(截至2018-12-25)！
foo[0..] # Get all chars starting at the first. Identical to foo[0..-1]
foo[-100..] # Get the last 100 characters页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/6423966
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