红宝石 - 如何从字符串中选择一些字符

Question

我想找到一个选择功能，例如：前100个字符串。在PHP中，存在substr function

Ruby是否有类似的功能？

Answer 1

尝试foo[0...100]，任何范围都可以。范围也可以消极。 Ruby的well explained in the documentation。

Answer 2

使用[] - 运算符：

foo[0,100] # Get the first 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) 

使用.slice方法：

foo.slice(0, 100) # Get the first 100 characters starting at position 0 
foo.slice(0...100) # All identical to [] 

并且为了完整性：

foo[0] # Returns the first character (doh!) 
foo[-100,100] # Get the last 100 characters in order. Negative index is 1-based 
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 character