在 Ruby 中声明变量？
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Declaring variables in Ruby?
提问by Alex Wilsen
When do I know when to declare a variable and not to in Ruby?
我什么时候知道什么时候声明一个变量而不是在 Ruby 中？
I would like to know why the first code needs input to be declared as a string and outside of the block, while the second block doesn't.
我想知道为什么第一个代码需要将输入声明为字符串并在块之外，而第二个块不需要。
input = ''
while input != 'bye'
puts input
input = gets.chomp
end
puts 'Come again soon!'
versus:
相对：
while true
input = gets.chomp
puts input
if input == 'bye'
break
end
end
puts 'Come again soon!'
回答by Gene
No variable is ever declared in Ruby. Rather, the rule is that a variable must appear in an assignment before it is used.
Ruby 中从未声明过任何变量。相反，规则是变量在使用之前必须出现在赋值中。
Look at the first two lines in your first example:
查看第一个示例中的前两行：
input = ''
while input != 'bye'
The whilecondition uses the variable input. Therefore the assignment is necessary before it. In the second example:
的while条件使用变量input。因此在它之前需要赋值。在第二个例子中：
while true
input = gets.chomp
puts input
Again, the variable inputis assigned before it is used in the putscall. All is right with the world in both examples.
同样，变量input在puts调用中使用之前被赋值。在这两个例子中，世界一切都好。
