问题
A silly, syntactical question:
If the assignment operator is really a function, like
def value=(x)
@value = x
end
without a space between the left-hand operand and the "=", then why can the assignment be made as test.value = x (with a space), but the method definition cannot be written as:
def value = (x)
@value = x
end
with the space. Is this simply syntax dictated by the parser?
回答1:
def needs to be followed by a token for the function name, optionally followed by an argument list. The parenthesis on the argument list is optional (e.g., def value= x is an appropriate definition). def value = (x) looks like def followed by two tokens and then an argument list, which does not parse.
回答2:
That's parser/interpreter magic.
When the interpreter sees the assignment looks for a matching method.
I agree with you in this regard ( almost ), I think the assignment should be some.value= x ( without space between 'value' and '=' ) always.
Scala does something similar but uses an underscore def value_= ( x: X )
来源：https://stackoverflow.com/questions/4963427/ruby-assignment-syntax