“！"的目的是什么?和“?"在方法名称的末尾? [英] What is the purpose of "!" and "?" at the end of method names?

问题描述

有时我在Ruby中看到带有?"的方法和 "！"在它们的末尾，例如:

Sometimes I see methods in Ruby that have "?" and "!" at the end of them, e.g:

name = "sample_string"
name.reverse
name.reverse!
name.is_binary_data?

我想知道他们的目的是什么?它们只是语法糖衣吗?

I was wondering what their purpose is? Are they just syntax sugarcoating?

推荐答案

出于可读性考虑，它只是糖衣"，但它们确实具有共同的含义:

It's "just sugarcoating" for readability, but they do have common meanings:

• 以!结尾的方法会执行某些永久性或潜在危险的更改；例如:
  • Enumerable#sort返回对象的排序版本，而Enumerable#sort!对其进行排序.
  • 在Rails中，如果保存失败，ActiveRecord::Base#save返回false，而ActiveRecord::Base#save!引发异常.
  • Kernel::exit导致脚本退出，而Kernel::exit!立即退出脚本，绕过所有退出处理程序.
  • Methods ending in ! perform some permanent or potentially dangerous change; for example:
    • Enumerable#sort returns a sorted version of the object while Enumerable#sort! sorts it in place.
    • In Rails, ActiveRecord::Base#save returns false if saving failed, while ActiveRecord::Base#save! raises an exception.
    • Kernel::exit causes a script to exit, while Kernel::exit! does so immediately, bypassing any exit handlers.

    在您的示例中，name.reverse求值为反向字符串，但仅在name.reverse!行之后，name变量才实际包含反向名称. name.is_binary_data?看起来像是"name二进制数据吗?".

    In your example, name.reverse evaluates to a reversed string, but only after the name.reverse! line does the name variable actually contain the reversed name. name.is_binary_data? looks like "is name binary data?".

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