find method in rails

without dynamic find_by_all

@task = Task.find( :all, :conditions=> [‘complete= ?’ ,false] )

with dynamic find_by_all

@task = Task.find_all_by_complete(false)

without dynamic find_by

@task = Task.find( :first, :conditions=> [‘complete= ?’ ,false],

                                :order=>’created_at DESC’ )

with dynamic find_by

@task = Task.find_by_complete(false,   :order=>’created_at DESC’)

find by id

find( params[:id], :conditions=>[“name=?”, “peter” ] )

find through association

ex:

project has many tasks

task belongs to project

without association:

@task = Task.find(:all, :conditions=> [ ‘proect_id=? AND complete =?’  , @project_id,  false] )

with association:

@project = Project.find(params[:id])

@task = @project.tasks.find(:all,     :conditions=>[‘complete=?’,   false])

or

@task = @project.tasks.find_all_by_complete(false) 

find method in model

將find method定義在model比較好

ex:

Task的model

def  self.find_incompletet 

    find_all_by_complete(false, :order=>’created_at DESC’ )

end    

 注意: 此find method要定義成class method

          到時候可呼叫 @project.tasks.find_incomplete

          若定義成instance method，則會error

find_by_sql:

use sql syntax in the find_by_sql

pros:  faster