In the rails application, when the table structure is complex, i often have
many ways to access the database to get the data, such as using several
attributes.
For example,
table :person
column :nickname
column :hobbies
column :constellation
...........
I have to write several methods to fit for the requirement. For example,
get_personal_by_nickname, get_personal_by_nickname_with_hobbies, so on.
So I wrote a function, using a condition map to do the mapping. like
module ActiveRecord
class Base
class << self
# generate the query conditions due to the CMAP
def generate_query(options = {})
includes, conditions = Array.new, Array.new
options.each do |key, value|
begin
if (@CMAP.has_key?(key) && !value.nil?)
case @CMAP[key][0]
when Symbol
includes << @CMAP[key][0]
when Hash
includes << @CMAP[key][0][value.to_sym]
end
case @CMAP[key][1]
when String
conditions << @CMAP[key][1] if @CMAP[key][1]
when Hash
conditions << @CMAP[key][1][value.to_sym] if @CMAP[key][1]
end
end
rescue NameError
$stderr.print "you should define @CMAP attribute for the
query_generator" + $!
raise
end
end
[includes, conditions]
end
end
In the specific model, @CMAP is defined as, for example,
@CMAP = {
:nickname => [:include, "nickname = :nickname"],
:hobbies => [:include, "hobbies = :hobbies"],
...........
}
Then using hash as a param and get the generated query.
But this way i need to take care of @CMAP, indeed sometimes it can''t
fit my
requirement either.
Is there a better way to do the work? How do you guys work this?
thx.
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> I have to write several methods to fit for the requirement. For example, > get_personal_by_nickname, get_personal_by_nickname_with_hobbies, so on.Are you aware of the build-in dynamic attribute-based finders (although this might not cover all possible uses of you method)? e.g. User.find_by_username_and_password( usrname, pw ) is equal to User.find :first, :conditions => ["username = ? AND password = ?", usrname, pw] read more: http://api.rubyonrails.org/classes/ActiveRecord/Base.html regards, _jan --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 8/4/07, jeanmartin <jan.schwenzien-Mmb7MZpHnFY@public.gmane.org> wrote:> > > > > I have to write several methods to fit for the requirement. For example, > > get_personal_by_nickname, get_personal_by_nickname_with_hobbies, so on. > > Are you aware of the build-in dynamic attribute-based finders > (although this might not cover all possible uses of you method)?No. The query may be complex. for example, include several tables. I need to generate the condition dynamically. e.g.> User.find_by_username_and_password( usrname, pw ) > is equal to > User.find :first, :conditions => ["username = ? AND password = ?", > usrname, pw] > > read more: http://api.rubyonrails.org/classes/ActiveRecord/Base.html > > regards, _jan > > > > >--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
> > > I have to write several methods to fit for the requirement. For example, > > > get_personal_by_nickname, get_personal_by_nickname_with_hobbies, so on. > > > Are you aware of the build-in dynamic attribute-based finders > > (although this might not cover all possible uses of you method)? > > No. The query may be complex. for example, include several tables. I need > to > generate the condition dynamically.Then -for me- it depends on the complexity: - For time consuming tasks i try to solve it inside the db: stored procedures, views etc. - If there are not too many different querys I create model methods (like find_most_active_members()) - In general the find method provides almost all possibly needed options for sql queries (are you sure it doesn''t fit your needs? You can :include => other_tables, define :conditions, set a :limit and :offset etc.( Maybe you could provide us with an example of one of your complex queries. regards, _jan --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 8/4/07, jeanmartin <jan.schwenzien-Mmb7MZpHnFY@public.gmane.org> wrote:> > > > > > I have to write several methods to fit for the requirement. For > example, > > > > get_personal_by_nickname, get_personal_by_nickname_with_hobbies, so > on. > > > > > Are you aware of the build-in dynamic attribute-based finders > > > (although this might not cover all possible uses of you method)? > > > > No. The query may be complex. for example, include several tables. I > need > > to > > generate the condition dynamically. > > Then -for me- it depends on the complexity: > - For time consuming tasks i try to solve it inside the db: stored > procedures, views etc. > - If there are not too many different querys I create model methods > (like find_most_active_members()) > - In general the find method provides almost all possibly needed > options for sql queries (are you sure it doesn''t fit your needs? You > can :include => other_tables, define :conditions, set a :limit > and :offset etc.(Yes. I can. But i''m lazy... :( I want a common place to combine the query for me. Let me take a example. Book Model has_many :authors has_many :tags belong_to :category has_many :readers get_book(params) params maybe author_name, or tag_name, or category_name, or reader_name, or mixed. With different options, the includes array and conditions are different. I don''t want to repeat the code, instead i want a way to directly turn the params to the condition. So as in other model. That''s why i thought of my last design as in my first post. Maybe you could provide us with an example of one of your complex> queries. > > regards, _jan > > > > >--~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
A strategy I have employed on similar tasks is to model the queries as
objects, e.g.:
class EventQuery
def self.from_params(params)
...
end
def find_events
...
end
end
It tends to encapsulate things fairly nicely. In my app, I also had the
need to store the queries in the database, so I went further and
subclassed ActiveRecord::Base.
- donald
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