Ruby 中方法名称的限制是什么? [英] What are the restrictions for method names in Ruby?
问题描述
例如，我在下面的代码片段中找到了方法名称 bundler?，但不知道 ? 字符是专用关键字还是只是其中的一部分方法名称.
For example, I found the method name bundler? in the following snippet, and don't know whether the ? character is a specialized keyword or just part of the method name.
# This is a predicate useful for the doc:guides task of applications.
def bundler?
# Note that rake sets the cwd to the one that contains the Rakefile
# being executed.
File.exists?('Gemfile')
end
推荐答案
Ruby 中的方法名称可以包含大小写字母、数字、下划线 _ 和标点符号 !、?、=.
Method names in Ruby may contain upper-case and lower-case letters, numbers, underscores _ and the punctation signs !, ?, =.
方法名不能以数字开头，字符!、?和=只能出现在末尾.
A method name can't begin with a number, and the characters !, ? and = can only appear at the end.
可以在方法名称中使用非 ASCII 字符，但这会导致非常混乱的情况，不应该是常见的做法.
Non-ASCII characters can be used in a method name, but this can lead to very confusing situations and should not be common practice.
以小写字符开头的方法名称虽然不是强制性的，但这是一种很好的做法，因为以大写字母开头的名称在 Ruby 中是常量.仍然可以为方法使用常量名称，但您将无法在没有括号的情况下调用它，因为 interpeter 会将名称作为常量进行查找:
It's good practice, while not mandatory, to start the method name with a lower-case character, because names that start with capital letters are constants in Ruby. It's still possible to use a constant name for a method, but you won't be able to invoke it without parentheses, because the interpeter will look-up for the name as a constant:
def Capital
nil
end
Capital # NameError: uninitialized constant Capital
Capital() # => nil
在定义方法名称时，一些非常广泛且一致使用的约定是:
Some very widely and consistently used conventions when defining method names are:
方法名称全部小写，下划线
_作为名称中单词的分隔符(例如Math::sqrt、Array#each_index, ...).
Method names are full down-case, with underscores
_as separators for words into the name (e.g.Math::sqrt,Array#each_index, ...).
谓词有一个问号 ? 作为最后一个字符(例如 Array#empty?、Hash#has_key?, ...).虽然谓词通常返回布尔值，但情况并非总是如此:如果谓词评估为假，这些方法只需要返回 nil 或 false，否则返回任何其他值(例如File::size? 返回 nil 如果文件不存在，文件的大小为 Integer 否则).
Predicates have a question mark ? as last character (e.g. Array#empty?, Hash#has_key?, ...). While predicates usually return boolean values, this is not always the case: these methods just need to return nil or false if the predicate evaluates to false, any other value otherwise (e.g. File::size? returns nil if the file does not exist, the size of the file as an Integer otherwise).
修改被调用对象状态的方法，或具有异常行为的方法的最后一个字符是感叹号!；这种方法有时被称为 mutators 因为它们通常是其他方法的破坏性或就地版本(例如 Array#sort!、Array#slice!, ...).
Methods that modify the state of the object on which they are invoked, or that have an unusual behavior have an exclamation mark ! as last character; this methods are sometimes called mutators because they usually are destructive or in-place versions of other methods (e.g. Array#sort!, Array#slice!, ...).
Setters 有一个等号 = 作为最后一个字符(例如 Array#[]=, ...)；Ruby interpeter 为调用 setter 方法提供了语法糖:
Setters have an equal sign = as last character (e.g. Array#[]=, ...); the Ruby interpeter offers syntactic sugar for invokation of setter methods:
a = [4, 5, 6]
a[0] = 3 # Shorthand for a.[]=(0, 3)
Ruby 还允许使用运算符符号作为方法名称来定义运算符:
Ruby also allows to define operators using the operator symbol as the method name:
╔═══════════════════════════╦═════════════════════════════════════════════╦═══════╗
║ Operators (by precedence) ║ Operations ║ Arity ║
╠═══════════════════════════╬═════════════════════════════════════════════╬═══════╣
║ ! ~ + ║ Boolean NOT, bitwise complement, unary plus ║ 1 ║
║ ║ (define with method name +@, Ruby 1.9+) ║ ║
║ ║ ║ ║
║ ** ║ Exponentiation ║ 2 ║
║ ║ ║ ║
║ - ║ Unary minus (define with method name -@) ║ 1 ║
║ ║ ║ ║
║ * / % ║ Multiplication, division, modulo ║ 2 ║
║ ║ ║ ║
║ + - ║ Addition, subtraction ║ 2 ║
║ ║ ║ ║
║ << >> ║ Bitwise shift ║ 2 ║
║ ║ ║ ║
║ & ║ Bitwise AND ║ 2 ║
║ ║ ║ ║
║ | ^ ║ Bitwise OR, Bitwise XOR ║ 2 ║
║ ║ ║ ║
║ < <= => > ║ Ordering ║ 2 ║
║ ║ ║ ║
║ == === != =~ !~ <=> ║ Equality, pattern matching, comparison ║ 2 ║
╚═══════════════════════════╩═════════════════════════════════════════════╩═══════╝
一元运算符方法不传递参数；二元运算符方法传递一个参数，并对它和 self 进行操作.
Unary operator methods are passed no arguments; binary operator methods are passed an argument, and operate on it and on self.
严格遵守操作符的数量很重要；虽然可以定义具有不同数量的运算符方法(例如，带有两个参数的 + 方法)，但 Ruby 不允许您使用运算符语法调用该方法(但是它可以使用点语法).
It's important to adhere strictly to the arity of the operators; while it is possible to define operator methods with a different arity (e.g. a + method that takes two arguments), Ruby would not allow you to call the method with operator syntax (it would however work with dot syntax).
尽可能遵循运算符的原始语义是一种很好的做法:对于了解运算符原始含义的人来说，它应该是直观的.
It's good practice to adhere to the original semantics of the operators as much as possible: it should be intuitive to someone who knows the original meaning of the operator how it works with user defined classes.
该语言还为通常用于访问数组和哈希值的特殊非运算符、[] 方法提供了语法糖.[] 方法可以定义为任意数量.
The language also offers syntactic sugar for the special, non-operator ,[] method that is normally used for accessing array and hash values. The [] method can be defined with arbitrary arity.
对于表中的每个二元运算符，除了排序、相等、比较和模式匹配，Ruby 还提供了缩写赋值的简写(例如 x += y 扩展为 x = x +y);您不能将它们定义为方法，但您可以通过定义它们所基于的运算符来改变它们的行为.
For every binary operator in the table, except ordering, equality, comparison and pattern matching, Ruby also offers shorthand for abbreviated assignment (e.g. x += y expands to x = x + y); you can't define them as methods, but you can alter their behavior defining the operators on which they're based.
这些字符都不能在普通方法名称中使用(例如，do&print 或 start-up 不是有效的方法名称).
None of these characters can be used inside normal method names (e.g. do&print or start-up are not valid method names).
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