I''ll start off by saying I am new to Ruby and Rails...
Suppose I run the following;
$ script/generate model person
which creates:
class CreatePeople < ActiveRecord::Migration
def self.up
create_table :people do |t|
t.timestamps
end
end
def self.down
drop_table :people
end
end
I added in some code (the author instructs me to) such that it now
reads:
class CreatePeople < ActiveRecord::Migration
def self.up
create_table :people do |t|
t.string :name, :type, :email, :camera #ADDED IN
t.timestamps
end
end
def self.down
drop_table :people
end
end
I do not understand, at a ruby level, what is going on. It appears I
have a class (static) method called up. The first thing I am doing is
calling Migration''s create_table method. This leads to question 1:
1:) Migration does not have create_table method. How is Ruby finding
create_table?
Now the create_table method appears to accept two parameters. The first
being a symbol, and the second being a code block.
I am assuming that the only thing obtainable from this code block is the
last line t.timestamps, as the last line is returned in ruby.
So question number two:
2: What does this line even do?
t.string :name, :type, :email, :camera #ADDED IN
What is t being passed in? why no comma between t.string and :name.
And my final question...
How come I cannot write the code as follows (Aptana will not compile
it)?
def self.up
create_table (:people,{|t|
t.string :name, :type, :email, :camera
t.timestamps
})
end
BTW as I hunt I do see this in Migration:
def method_missing(method, *arguments, &block)
It is taunting me.
Feel free to respond to me like I am four. You could try to insult me
but you would fail :-)
Thanks,
Cris
--
Posted via http://www.ruby-forum.com/.
Cris Shupp wrote:> I''ll start off by saying I am new to Ruby and Rails...You might find it helpful to read about Ruby''s object model in general. It''s subtly different from those of most other OO languages.> > Suppose I run the following; > > $ script/generate model person > > > which creates: > > class CreatePeople < ActiveRecord::Migration > def self.up > create_table :people do |t| > > t.timestamps > end > end > > def self.down > drop_table :people > end > end > > > I added in some code (the author instructs me to) such that it now > reads: > > class CreatePeople < ActiveRecord::Migration > def self.up > create_table :people do |t| > t.string :name, :type, :email, :camera #ADDED IN > t.timestamps > end > end > > def self.down > drop_table :people > end > end > > I do not understand, at a ruby level, what is going on. It appears I > have a class (static) method called up.Correct.> The first thing I am doing is > calling Migration''s create_table method. This leads to question 1: > > 1:) Migration does not have create_table method.You''re right. But the DB connection adapters do.> How is Ruby finding > create_table?Presumably by delegating to the connection adapter, likely by means of method_missing.> > Now the create_table method appears to accept two parameters. The first > being a symbol, and the second being a code block. > > I am assuming that the only thing obtainable from this code block is the > last line t.timestamps, as the last line is returned in ruby. > > So question number two: > > 2: What does this line even do? > t.string :name, :type, :email, :camera #ADDED IN > > What is t being passed in?A block argument.> why no comma between t.string and :name.Because string is the name of the method being called on t , while :name is its first argument. With parentheses, it would be t.string(:name, :and_so_on) , but in Ruby, you can omit the parentheses when it would not be ambiguous.> > > And my final question... > > How come I cannot write the code as follows (Aptana will not compile > it)? > def self.up > create_table (:people,{|t| > t.string :name, :type, :email, :camera > t.timestamps > }) > endBecause you''ve got your syntax wrong. The braces aren''t correct In this context (this isn''t JavaScript!) and parens don''t go around blocks passed to functions. Aptana isn''t doing any compilation for you, BTW. (And on an unrelated note, the sooner you stop using an IDE for Rails, the better. I reccomend a good editor like KomodoEdit instead.)> > > BTW as I hunt I do see this in Migration: > > def method_missing(method, *arguments, &block) > > It is taunting me.What''s taunting you? Go learn about method_missing and how it works. It''s an important Ruby concept.> > Feel free to respond to me like I am four. You could try to insult me > but you would fail :-)I think you can answer many of your questions by looking at the Rails source and the remainder by reading Programming Ruby.> > Thanks, > > CrisBest, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
Marnen Laibow-Koser wrote:> Cris Shupp wrote:[...]>> How come I cannot write the code as follows (Aptana will not compile >> it)? >> def self.up >> create_table (:people,{|t| >> t.string :name, :type, :email, :camera >> t.timestamps >> }) >> end > > Because you''ve got your syntax wrong. The braces aren''t correct In this > context (this isn''t JavaScript!) and parens don''t go around blocks > passed to functions.[...] On second thought, the braces are probably OK (although it''s more common to use do...end for multiline blocks and braces for single-line ones). The bigger problem is the parentheses. If you''re going to use them, then the closing parenthesis goes *before* the beginning of the block. Best, -- Marnen Laibow-Koser http://www.marnen.org marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org -- Posted via http://www.ruby-forum.com/.
Marnen, Thanks! You answered my questions perfectly!!! Thanks, Cris Marnen Laibow-Koser wrote:> Marnen Laibow-Koser wrote: >> Cris Shupp wrote: > [...] >>> How come I cannot write the code as follows (Aptana will not compile >>> it)? >>> def self.up >>> create_table (:people,{|t| >>> t.string :name, :type, :email, :camera >>> t.timestamps >>> }) >>> end >> >> Because you''ve got your syntax wrong. The braces aren''t correct In this >> context (this isn''t JavaScript!) and parens don''t go around blocks >> passed to functions. > [...] > > On second thought, the braces are probably OK (although it''s more common > to use do...end for multiline blocks and braces for single-line ones). > The bigger problem is the parentheses. If you''re going to use them, > then the closing parenthesis goes *before* the beginning of the block. > > Best, > -- > Marnen Laibow-Koser > http://www.marnen.org > marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org-- Posted via http://www.ruby-forum.com/.
Oh and this does work, not around the block as you said:
def self.up
create_table (:people) { |t|
t.string :name, :type, :email, :camera
t.timestamps
}
end
Thanks again!
Cris Shupp wrote:> Marnen,
>
> Thanks! You answered my questions perfectly!!!
>
> Thanks,
>
> Cris
>
> Marnen Laibow-Koser wrote:
>> Marnen Laibow-Koser wrote:
>>> Cris Shupp wrote:
>> [...]
>>>> How come I cannot write the code as follows (Aptana will not
compile
>>>> it)?
>>>> def self.up
>>>> create_table (:people,{|t|
>>>> t.string :name, :type, :email, :camera
>>>> t.timestamps
>>>> })
>>>> end
>>>
>>> Because you''ve got your syntax wrong. The braces
aren''t correct In this
>>> context (this isn''t JavaScript!) and parens don''t
go around blocks
>>> passed to functions.
>> [...]
>>
>> On second thought, the braces are probably OK (although it''s
more common
>> to use do...end for multiline blocks and braces for single-line ones).
>> The bigger problem is the parentheses. If you''re going to use
them,
>> then the closing parenthesis goes *before* the beginning of the block.
>>
>> Best,
>> --
>> Marnen Laibow-Koser
>> http://www.marnen.org
>> marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
--
Posted via http://www.ruby-forum.com/.