Ruby on Rails

On Wed, Feb 20, 2013 at 3:25 PM, Colin Law <clanlaw@googlemail.com> wrote:
> On 20 February 2013 17:57, Jason Hsu, Android developer
> <jhsu802701@gmail.com> wrote:
>> I have a function defined as follows:
>>
>> def download_file (url1, url2, file1, file_age_max_hours)
>> puts (url1)
>> puts (url2)
>> puts (file1)
>> puts (file_age_max_hours)
>> end
>>
>> The following command works:
>> download_file("Hello", "World", "Rubyists", 34)
>>
>> The following command fails:
>> download_file ("Hello", "World", "Rubyists", 34)
>>
>> The only difference is the space before the "(". Why is the presence or
>> absence of this space so significant? This was never a problem for me in
>> Python. (On the other hand, I quickly learned to NEVER use tabs to indent
>> when programming in Python.)
>
> Because this is Ruby not Python. My understanding of why this is so
> (which may be wrong or at least incomplete) is because you do not need
> the parentheses at all, so you could say
> download_file "Hello", "World", "Rubyists", 34
> so if you have a space and a "(" then the space starts the parameter
> list and then along comes a "(" which may now have a different
> meaning, dependant on context. So the best thing is just to remember
> not to put a space after the method name if you are using parentheses.

the space + () creates a new closure and that closure causes an error
because you have a bunch of commas outside of context. Colin is
right, I just wanted to elaborate that it creates a new closure.

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