Ruby 中的 to_s 与 to_str(以及 to_i/to_a/to_h 与 to_int/to_ary/to_hash) [英] to_s vs. to_str (and to_i/to_a/to_h vs. to_int/to_ary/to_hash) in Ruby

问题描述

我正在学习 Ruby，我看到了一些让我有点困惑的方法，特别是 to_s 与 to_str(类似地，to_i/to_int, to_a/to_ary, & to_h/to_hash>).我读过的内容解释说，较短的形式(例如 to_s)用于显式转换，而较长的形式用于隐式转换.

I'm learning Ruby and I've seen a couple of methods that are confusing me a bit, particularly to_s vs to_str (and similarly, to_i/to_int, to_a/to_ary, & to_h/to_hash). What I've read explains that the shorter form (e.g. to_s) are for explicit conversions while the longer form are for implicit conversions.

我真的不明白 to_str 将如何实际使用.除了 String 之外的其他东西会定义 to_str 吗?你能给出这个方法的实际应用吗?

I don't really understand how to_str would actually be used. Would something other than a String ever define to_str? Can you give a practical application for this method?

推荐答案

首先请注意，所有这些都适用于每一对短"(例如 to_s/to_i/to_a/to_h) 与long"(例如 to_str/to_int/to_ary)code>/to_hash) Ruby 中的强制方法(针对它们各自的类型)，因为它们都具有相同的语义.

Note first that all of this applies to each pair of "short" (e.g. to_s/to_i/to_a/to_h) vs. "long" (e.g. to_str/to_int/to_ary/to_hash) coercion methods in Ruby (for their respective types) as they all have the same semantics.

它们有不同的含义.你不应该实现 to_str 除非你的对象 像一个字符串一样作用，而不是仅仅被一个字符串表示.实现 to_str 的唯一核心类是 String 本身.

They have different meanings. You should not implement to_str unless your object acts like a string, rather than just being representable by a string. The only core class that implements to_str is String itself.

来自 Programming Ruby(引自 这篇博文，值得一读):

From Programming Ruby (quoted from this blog post, which is worth reading all of):

[to_i 和 to_s] 并不是特别严格:例如，如果一个对象有某种像样的字符串表示，它可能会有一个 to_s 方法... [to_int 和 to_str] 是严格的转换函数:只有当 [your] 对象可以自然地在每个地方使用字符串或可以使用整数.

[to_i and to_s] are not particularly strict: if an object has some kind of decent representation as a string, for example, it will probably have a to_s method… [to_int and to_str] are strict conversion functions: you implement them only if [your] object can naturally be used every place a string or an integer could be used.

来自 Pickaxe 的旧 Ruby 文档 有这个说:

与几乎所有类都支持的 to_s 不同，to_str 通常仅由那些行为类似于字符串的类实现.

Unlike to_s, which is supported by almost all classes, to_str is normally implemented only by those classes that act like strings.

例如，除了 Integer 之外，浮动 &Numeric 实现 to_int (to_i 相当于 to_str)，因为它们都可以很容易地替换为一个整数(它们实际上都是数字).除非您的类与 String 具有类似的紧密关系，否则您不应实现 to_str.

For example, in addition to Integer, both Float & Numeric implement to_int (to_i's equivalent of to_str) because both of them can readily substituted for an Integer (they are all actually numbers). Unless your class has a similarly tight relationship with String, you should not implement to_str.

这篇关于Ruby 中的 to_s 与 to_str(以及 to_i/to_a/to_h 与 to_int/to_ary/to_hash)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！