Rails 3中的字符串串联 [英] String concatenation in Rails 3

问题描述

我想知道为什么会这样：如果加号和下一个字符串之间有空格，则Ruby将两个字符串连接起来。但是如果没有空间，是否会应用一元运算符？

I'm wondering why this is so: Ruby concatenates two strings if there is a space between the plus and the next string. But if there is no space, does it apply some unary operator?

params['controller'].to_s + '/'
# => "posts/"

params['controller'].to_s +'/'
# => NoMethodError: undefined method `+@' for "/":String

推荐答案

解析器将 +'/'解释为 to_s 方法调用的第一个参数。它将这两个语句视为等效：

The parser is interpreting +'/' as the first parameter to the to_s method call. It is treating these two statements as equivalent:

> params['controller'].to_s +'/'
# NoMethodError: undefined method `+@' for "/":String

> params['controller'].to_s(+'/')
# NoMethodError: undefined method `+@' for "/":String

如果在 to_s 方法调用的末尾显式包括括号，则问题将消失：

If you explicitly include the parenthesis at the end of the to_s method call the problem goes away:

> params['controller'].to_s() +'/'
=> "posts/"

这篇关于Rails 3中的字符串串联的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！