Newbie: How to refer to 'this' instance's items

Hi,

I’ve been playing with Rails for a few months now and I enjoying it. But
most recently, I’ve just come across an issue that I just can’t seem to
resolve, to the point where I’ve recreated a small application from
scratch to reproduce the issue (and I’m confident the problem is with me
not knowing the language well enough).

Here’s the issue…

I have ACCOUNTS that hold zero or more OPERATIONS. Each OPERATION has a
FROM ACCOUNT and a TO ACCOUNT (think accounting). See below for some
schema information.

Here’s the code for the account.rb model:

class Account < ActiveRecord::Base
has_many :operations, :order => “actual_date”
def has_operations?
#
# The problem is the “???” what do I replace them with?
# :id doesn’t work
# @id doesn’t work wither
# self.id doesn’t work
#
if ( Operation.find_by_from_account_id( ??? ).size > 0 ||
Operation.find_by_to_account_id( ??? ).size > 0 )
return true
else
return false
end
end
end

And here’s my show.rhtml

<% for column in Account.content_columns %>

<%= column.human_name %>: <%=h @account.send(column.name) %>

<% end %>

<% if @account.has_operations? %>

Operations

<% for operation in @account.expenses %> <% end %>
<%= operation.actual_date %><%= link_to 'Show', :action => 'show', :id => operation %> <%= link_to 'Edit', :action => 'edit', :id => operation %> <%= link_to 'Destroy', { :action => 'destroy', :id => operation }, :confirm => 'Are you sure?', :method => :post %>
<% end %> <%= link_to 'Edit this account', :action => 'edit', :id => @account %> | <%= link_to 'Return to list', :action => 'list' %>

Now the above works if I remove the “has_operations?” method from my
“account.rb” file AND my Operations table looks like this:

create_table “operations”, :force => true do |t|
t.column “actual_date”, :datetime
t.column “amount”, :decimal
t.column “account_id”, :integer
t.column “to_recipient”, :string
end

*Notice the “account_id” instead of “to_account_id” and
“from_account_id”.

As Rails is nice enough to understand the “has_many” and “belongs_to”
relationships. But when I change “account_id” to “from_account_id” and
“to_account_id”;

create_table “operations”, :force => true do |t|
t.column “actual_date”, :datetime
t.column “amount”, :decimal
t.column “from_account_id”, :integer
t.column “to_account_id”, :integer
end

the dynamically generated “has_operations?” method shits to bed as it
cannot find “account_id” (makes sense). So I replace it (maybe there’s
another way) with the version shown above. This new method gets called
directly from the “show.rhtml” file and all I need from the instance is
the “id” – which Rails discovers and uses in it’s own “has_operations?”
method when it generates it, but I can’t seem to get to with my
version…

Your help would be much appreciated!

Thanks!

Marc :o)

On 8/21/07, Marc B. [email protected] wrote:

Here’s the issue…
#
end

%>

As Rails is nice enough to understand the “has_many” and “belongs_to”
the dynamically generated “has_operations?” method shits to bed as it

Marc :o)

Marc

I believe you’re finding it difficult because your associations aren’t
quite
setup right.

If you want to use from_account_id and to_account_it in operations, this
suggests two assocaitions

You might model it something like this.

class Account < ActiveRecord::Base

has_many :operations_from, :class_name => “Operations”, :foreign_key
=>
“from_account_id”, :order => “actual_date”
has_many :operations_to, :class_name => “Operations”, :foreign_key =>
“to_account_id”, :order => “actual_date”

def has_operations?
operations_from.count > 0 || operations_to.count > 0
end
end

When you’re inside the account model you shouldn;t use Operation.find
class
methods much if at all. You should use the assocation methods setup by
the
has_many and belongs to.

You should use this version of your migrations for this.

create_table “operations”, :force => true do |t|
t.column “actual_date”, :datetime
t.column “amount”, :decimal
t.column “from_account_id”, :integer
t.column “to_account_id”, :integer
end

You should setup the belongs_to call similarly to the has_many

HTH
Daniel

Daniel ----- wrote:

On 8/21/07, Marc B. [email protected] wrote:

Here’s the issue…
#
end

%>

As Rails is nice enough to understand the “has_many” and “belongs_to”
the dynamically generated “has_operations?” method shits to bed as it

Marc :o)

Marc

I believe you’re finding it difficult because your associations aren’t
quite
setup right.

If you want to use from_account_id and to_account_it in operations, this
suggests two assocaitions

You might model it something like this.

class Account < ActiveRecord::Base

has_many :operations_from, :class_name => “Operations”, :foreign_key
=>
“from_account_id”, :order => “actual_date”
has_many :operations_to, :class_name => “Operations”, :foreign_key =>
“to_account_id”, :order => “actual_date”

def has_operations?
operations_from.count > 0 || operations_to.count > 0
end
end

When you’re inside the account model you shouldn;t use Operation.find
class
methods much if at all. You should use the assocation methods setup by
the
has_many and belongs to.

You should use this version of your migrations for this.

create_table “operations”, :force => true do |t|
t.column “actual_date”, :datetime
t.column “amount”, :decimal
t.column “from_account_id”, :integer
t.column “to_account_id”, :integer
end

You should setup the belongs_to call similarly to the has_many

HTH
Daniel

Thanks so much Daniel! :o)

My Rails inexperience shows. I coded for 15 years (C, C++, Java) and
after a 6 year break – leading and managing J2EE development teams –
I’ve rediscovered programming through Ruby on Rails and I’m having a
blast (too bad I can only spend 3-4 hours a week on this).

Have a good one!

Marc

On 8/21/07, Marc B. [email protected] wrote:

As Rails is nice enough to understand the “has_many” and “belongs_to”
quite
has_many :operations_from, :class_name => “Operations”, :foreign_key
When you’re inside the account model you shouldn;t use Operation.find
t.column “from_account_id”, :integer

My Rails inexperience shows. I coded for 15 years (C, C++, Java) and
after a 6 year break – leading and managing J2EE development teams –
I’ve rediscovered programming through Ruby on Rails and I’m having a
blast (too bad I can only spend 3-4 hours a week on this).

Have a good one!

Marc

Yeah Ruby’s great. I really like it but I don’t get enough time on it
either :wink:

Glad I could help.

-Daniel

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