为什么在Ruby方法中使用感叹号? [英] Why are exclamation marks used in Ruby methods?

问题描述

在Ruby中，某些方法带有问号(?)，它会问类似include?的问题，询问是否包含所讨论的对象，然后返回true/false.

In Ruby some methods have a question mark (?) that ask a question like include? that ask if the object in question is included, this then returns a true/false.

但是为什么有些方法带有感叹号(!)而其他方法没有呢?

But why do some methods have exclamation marks (!) where others don't?

这是什么意思?

推荐答案

通常，以!结尾的方法表示该方法将修改其调用的对象. Ruby将它们称为"危险方法"，因为它们会更改其他人可能引用的状态.这是一个简单的字符串示例:

In general, methods that end in ! indicate that the method will modify the object it's called on. Ruby calls these as "dangerous methods" because they change state that someone else might have a reference to. Here's a simple example for strings:

foo = "A STRING"  # a string called foo
foo.downcase!     # modifies foo itself
puts foo          # prints modified foo

这将输出:

a string

在标准库中，您会在很多地方看到成对的相似命名的方法，一个带有!，另一个没有.那些没有的方法称为安全方法"，它们将返回原始副本，并且对副本进行更改，而被调用方则保持不变.这是不带!的相同示例:

In the standard libraries, there are a lot of places you'll see pairs of similarly named methods, one with the ! and one without. The ones without are called "safe methods", and they return a copy of the original with changes applied to the copy, with the callee unchanged. Here's the same example without the !:

foo = "A STRING"    # a string called foo
bar = foo.downcase  # doesn't modify foo; returns a modified string
puts foo            # prints unchanged foo
puts bar            # prints newly created bar

这将输出:

A STRING
a string

请记住，这只是一个约定，但是遵循许多Ruby类.它还可以帮助您跟踪代码中正在修改的内容.

Keep in mind this is just a convention, but a lot of Ruby classes follow it. It also helps you keep track of what's getting modified in your code.

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