Parentheses vs braces

Rails
1

Working thru a Rails tutorial…

Can anyone tell me why the first example uses braces and the second
example uses parentheses? Is it because 1st example is a hash literal,
second is not?

u = User.find(2)
u.attributes = {:name =>“Fred”, :color => “green”}
u.save

u = User.find(2)
u.update_attributes(:name =>“Fred”, :color => “green”)

2

Someone can correct me if I’m wrong, but the second example actually is
a
hash. You wrote:

u.update_attributes(:name =>“Fred”, :color => “green”)

The arguments you passed in are a hash. It’s the same thing as writing:

u.update_attributes({:name =>“Fred”, :color => “green”})

Ruby (I think…or is it Rails?) gives you the freedom that if the
‘last’
parameter passed to a method is a hash, you can omit the { } characters.

3

So why the = sign in the first example?

4

u.update_attributes(…) is a method and you give it a hash as
parameter
u.attributes = … just assigns the attributes variable with a hash.

Den onsdagen den 25:e april 2012 kl. 21:15:36 UTC+2 skrev Ruby-Forum.com
User:

5

Ruby (I think…or is it Rails?) gives you the freedom that if the ‘last’
parameter passed to a method is a hash, you can omit the { } characters.

It’s Ruby. If the last argument in a function call is a hash, you can
omit
the braces.

6

On 25 April 2012 20:15, Dave C. [email protected] wrote:

So why the = sign in the first example?

Do you mean in
u.attributes = {:name =>“Fred”, :color => “green”}

Because that is assigning the hash to the variable u.attributes.

Please quote the previous message when replying in order to avoid the
necessity of looking back at previous emails to work out what the
message is referring to.

Colin

7

Leandro Facchinetti wrote in post #1058817:

It’s Ruby. If the last argument in a function call is a hash, you can
omit
the braces.

I think technically it has to do with ambiguity. It doesn’t really have
anything do with it being the last argument, but rather omitting the
braces anywhere else in the argument list would cause ambiguity.
Although, that’s really just semantics.