在 Ruby 中构建字符串时，为什么铲运算符 (<<) 比加等号 (+=) 更受欢迎? [英] Why is the shovel operator (<<) preferred over plus-equals (+=) when building a string in Ruby?

问题描述

我正在研究 Ruby Koans.

I am working through Ruby Koans.

about_strings.rb 中的 test_the_shovel_operator_modifying_the_original_string Koan 包含以下注释:

The test_the_shovel_operator_modifies_the_original_string Koan in about_strings.rb includes the following comment:

Ruby 程序员倾向于使用铲运算符 (<<) 而不是加号构建字符串时等于运算符 (+=).为什么?

Ruby programmers tend to favor the shovel operator (<<) over the plus equals operator (+=) when building up strings. Why?

我的猜测是它涉及速度，但我不明白引擎盖下的动作会导致铲子操作员更快.

My guess is it involves speed, but I don't understand the action under the hood that would cause the shovel operator to be faster.

有人能解释一下这个偏好背后的细节吗?

Would someone be able to please explain the details behind this preference?

推荐答案

证明:

a = 'foo'
a.object_id #=> 2154889340
a << 'bar'
a.object_id #=> 2154889340
a += 'quux'
a.object_id #=> 2154742560

所以 << 改变原始字符串而不是创建一个新字符串.这样做的原因是在 ruby​​ 中 a += b 是 a = a + b 的语法简写(其他 = 运算符)，这是一个赋值.另一方面，<< 是 concat() 的别名，它就地改变了接收者.

So << alters the original string rather than creating a new one. The reason for this is that in ruby a += b is syntactic shorthand for a = a + b (the same goes for the other <op>= operators) which is an assignment. On the other hand << is an alias of concat() which alters the receiver in-place.

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