I need a way to set a counter that will show how many of the model
have been created and put this in each instance. This will allow me to
use the record number as an input to another field before id is set.
After things are settled, the real id number can be substituted for
the counter.

I've tried new in the controller, but that's for a create action from
the app.


Thanks
Bob

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Search Discussions

  • Colin Law at Feb 8, 2012 at 9:40 am

    On 8 February 2012 07:12, Bob Smith wrote:
    I need a way to set a counter that will show how many of the model
    have been created and put this in each instance. This will allow me to
    use the record number as an input to another field before id is set.
    After things are settled, the real id number can be substituted for
    the counter.
    If you do that and two users come along at the same time and make new
    objects then they will both get the same number. Can you not just use
    a before_save filter to set the field? If you think not can you
    explain what you are trying to do (and why) in more detail as there is
    almost certainly a better solution.

    Colin

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  • Valery Kvon at Feb 8, 2012 at 11:32 am

    On 08.02.2012, at 13:39, Colin Law wrote:
    On 8 February 2012 07:12, Bob Smith wrote:
    I need a way to set a counter that will show how many of the model
    have been created and put this in each instance. This will allow me to
    use the record number as an input to another field before id is set.
    After things are settled, the real id number can be substituted for
    the counter.
    If you do that and two users come along at the same time and make new
    objects then they will both get the same number. Can you not just use
    a before_save filter to set the field? If you think not can you
    explain what you are trying to do (and why) in more detail as there is
    almost certainly a better solution.
    I think actually he asked about something counter-caching solution for stand-alone model/table. Good question, for the best approach it has to be realized on a database level. The second approach is to build additional caching table to keep counter values for anything you want. The last one is not so elegant.

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  • Peter Vandenabeele at Feb 8, 2012 at 12:11 pm

    On Wed, Feb 8, 2012 at 10:39 AM, Colin Law wrote:
    On 8 February 2012 07:12, Bob Smith wrote:
    I need a way to set a counter that will show how many of the model
    have been created and put this in each instance. This will allow me to
    use the record number as an input to another field before id is set.
    After things are settled, the real id number can be substituted for
    the counter.
    If you do that and two users come along at the same time and make new
    objects then they will both get the same number. Can you not just use
    a before_save filter to set the field? If you think not can you
    explain what you are trying to do (and why) in more detail as there is
    almost certainly a better solution.
    Maybe the OP really wants a "sequence" (a guaranteed unique number
    that is more or less monotomically going up).

    The OP may be used to the concept that the primary ID of a record upon
    creation is such a sequence. But maybe he needs that number _before_
    the record is saved. (e.g. to set a serial number that is saved in the
    record).

    If that is the business requirement, 3 solutions:

    1) don't do it that way. Use a separate sequence generator (which exists
    in Postgresql and probably in all databases) and use that to calculate
    the unique and more or less monoticly increasing serial number. Do NOT
    couple that "business id" with the actual internal database id.

    2) If you want to use the database id, then you could use an external
    sequence generator and set the Object.id manually before saving (than
    configure your db in a way that the primary key is set from the
    application).

    3) do an after_create (create the object with most data filled in, the
    create will generate the database id and in the after_create calculate
    the other field (e.g. serial number) and save again ... this is then an
    "update" so the "after_create" will not be triggered again). You may
    need some more tricks to make sure this "serial number" field cannot
    be modified, otherwise it could be out of sync with you internal database
    id (that is "back to (1) above" don't link the "serial number" with the
    database id, just make it a separate column with a unique index and
    use a separate sequencer to generate those unique codes).

    HTH,

    Peter

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  • Bob Smith at Feb 9, 2012 at 4:55 am

    On Feb 8, 7:11 am, Peter Vandenabeele wrote:
    On Wed, Feb 8, 2012 at 10:39 AM, Colin Law wrote:
    On 8 February 2012 07:12, Bob Smith wrote:
    I need a way to set a counter that will show how many of the model
    have been created and put this in each instance. This will allow me to
    use the record number as an input to another field before id is set.
    After things are settled, the real id number can be substituted for
    the counter.
    If you do that and two users come along at the same time and make new
    objects then they will both get the same number.  Can you not just use
    a before_save filter to set the field?  If you think not can you
    explain what you are trying to do (and why) in more detail as there is
    almost certainly a better solution.
    Maybe the OP really wants a "sequence" (a guaranteed unique number
    that is more or less monotomically going up).

    The OP may be used to the concept that the primary ID of a record upon
    creation is such a sequence. But maybe he needs that number _before_
    the record is saved. (e.g. to set a serial number that is saved in the
    record).

    If that is the business requirement, 3 solutions:

    1) don't do it that way. Use a separate sequence generator (which exists
    in Postgresql and probably in all databases) and use that to calculate
    the unique and more or less monoticly increasing serial number. Do NOT
    couple that "business id" with the actual internal database id.

    2) If you want to use the database id, then you could use an external
    sequence generator and set the Object.id manually before saving (than
    configure your db in a way that the primary key is set from the
    application).

    3) do an after_create  (create the object with most data filled in, the
    create will generate the database id and in the after_create calculate
    the other field (e.g. serial number) and save again ... this is then an
    "update" so the "after_create" will not be triggered again). You may
    need some more tricks to make sure this "serial number" field cannot
    be modified, otherwise it could be out of sync with you internal database
    id (that is "back to (1) above" don't link the "serial number" with the
    database id, just make it a separate column with a unique index and
    use a separate sequencer to generate those unique codes).

    HTH,

    Peter
    It seems a bit of explanation is in order..

    after_create, after_initialize, and the database won't help me.. I
    need this value to be available as soon as new creates a new object in
    the view, before any saving. I have the logic set to do this with
    existing records. What I am trying to do is have a unique value set in
    each new record so that they can be part of a radio button list.

    This is how the new objects are created

    <%= link_to_function "Add a Person" do |page|
    page.insert_html :bottom, 'empty', :partial => 'shared/
    person', :locals => {:temp => @temp,:household => @household}, :object
    => Person.new
    end %>


    My app is used at the signup table of a foodbank. My app has a
    household record that has address, zip, phone, etc. This has a child
    model called people with.. guess what... people :> There are radio
    buttons referencing the record id next to each person where the head
    of household can be selected. This is where the problem lies. No
    problem with existing people, but new ones have no id yet. I have
    added a variable to the people model to hold a counter. I have the
    logic to look back at the record after save, find the id of the wanted
    record, and replace the counter with the correct value. Now all I need
    is a way to set the counter at each new record. Hope this makes it
    clearer.


    Thanks
    Bob

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  • Bob Smith at Feb 9, 2012 at 5:48 am

    On Feb 8, 11:54 pm, Bob Smith wrote:
    On Feb 8, 7:11 am, Peter Vandenabeele wrote:


    On Wed, Feb 8, 2012 at 10:39 AM, Colin Law wrote:
    On 8 February 2012 07:12, Bob Smith wrote:
    I need a way to set a counter that will show how many of the model
    have been created and put this in each instance. This will allow me to
    use the record number as an input to another field before id is set.
    After things are settled, the real id number can be substituted for
    the counter.
    If you do that and two users come along at the same time and make new
    objects then they will both get the same number.  Can you not just use
    a before_save filter to set the field?  If you think not can you
    explain what you are trying to do (and why) in more detail as there is
    almost certainly a better solution.
    Maybe the OP really wants a "sequence" (a guaranteed unique number
    that is more or less monotomically going up).
    The OP may be used to the concept that the primary ID of a record upon
    creation is such a sequence. But maybe he needs that number _before_
    the record is saved. (e.g. to set a serial number that is saved in the
    record).
    If that is the business requirement, 3 solutions:
    1) don't do it that way. Use a separate sequence generator (which exists
    in Postgresql and probably in all databases) and use that to calculate
    the unique and more or less monoticly increasing serial number. Do NOT
    couple that "business id" with the actual internal database id.
    2) If you want to use the database id, then you could use an external
    sequence generator and set the Object.id manually before saving (than
    configure your db in a way that the primary key is set from the
    application).
    3) do an after_create  (create the object with most data filled in, the
    create will generate the database id and in the after_create calculate
    the other field (e.g. serial number) and save again ... this is then an
    "update" so the "after_create" will not be triggered again). You may
    need some more tricks to make sure this "serial number" field cannot
    be modified, otherwise it could be out of sync with you internal database
    id (that is "back to (1) above" don't link the "serial number" with the
    database id, just make it a separate column with a unique index and
    use a separate sequencer to generate those unique codes).
    HTH,
    Peter
    It seems a bit of explanation is in order..

    after_create, after_initialize, and the database won't help me.. I
    need this value to be available as soon as new creates a new object in
    the view, before any saving. I have the logic set to do this with
    existing records. What I am trying to do is have a unique value set in
    each new record so that they can be part of a radio button list.

    This is how the new objects are created

    <%= link_to_function "Add a Person" do |page|
    page.insert_html :bottom, 'empty', :partial => 'shared/
    person', :locals => {:temp => @temp,:household => @household}, :object
    => Person.new
    end %>

    My app is used at the signup table of a foodbank. My app has a
    household record that has address, zip, phone, etc. This has a child
    model called people with.. guess what... people :> There are radio
    buttons referencing the record id next to each person where the head
    of household can be selected. This is where the problem lies. No
    problem with existing people, but new ones have no id yet. I have
    added a variable to the people model to hold a counter. I have the
    logic to look back at the record after save, find the id of the wanted
    record, and replace the counter with the correct value. Now all I need
    is a way to set the counter at each new record. Hope this makes it
    clearer.

    Thanks
    Bob
    Just ALMOST fixed this thanks to google..

    in person.rb
    def initialize(params = nil)
    super()
    self.hoh = $hoh
    $hoh = $hoh - 1
    end

    This will set the model to the value in $hoh and decrement it once,
    but after that the $hoh = $hoh - 1 won't execute. If I make more than
    1 record, all values are the same.. Please help!!


    Thanks
    Bob

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  • Hassan Schroeder at Feb 9, 2012 at 6:07 am

    On Wed, Feb 8, 2012 at 8:54 PM, Bob Smith wrote:

    What I am trying to do is have a *unique value* set in each new record
    See: http://rubygems.org/gems/uuid

    HTH!
    --
    Hassan Schroeder ------------------------ hassan.schroeder@gmail.com
    http://about.me/hassanschroeder
    twitter: @hassan

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  • Peter Vandenabeele at Feb 9, 2012 at 8:52 am

    On Thu, Feb 9, 2012 at 7:07 AM, Hassan Schroeder wrote:
    On Wed, Feb 8, 2012 at 8:54 PM, Bob Smith wrote:

    What I am trying to do is have a *unique value* set in each new record
    See: http://rubygems.org/gems/uuid
    Indeed.

    And maybe better to not mess with the `def initialize`, but use the
    `after_initialize` function that is provided by Rails. I did it like this.


    ../lib/uuid_helper.rb

    require 'uuidtools'

    module UUIDHelper
    extend ActiveSupport::Concern

    included do
    after_initialize :set_uuid
    def set_uuid
    unless uuid # Note 1 below
    self.uuid = UUIDTools::UUID.random_create.to_s
    end
    end
    end
    end

    ../app/model/person.rb

    class Person < ActiveRecord::Base

    # UUID
    include UUIDHelper
    ...
    end

    Note 1:
    Be careful, it is a little tricky to _only_ set the value of the uuid
    when it is not yet present, otherwise reading back the value
    from the database will build a new instance of Person with a
    new random uuid. The code above is well tested and works.

    Maybe you will also need to add ../lib to your default load path.
    In config/application.rb

    # Custom directories with classes and modules you want to be
    autoloadable.
    config.autoload_paths += %W(#{config.root}/lib)
    config.autoload_paths += Dir["#{config.root}/lib/**/"]


    HTH,

    Peter

    *** Available for a new project ***

    Peter Vandenabeele
    http://twitter.com/peter_v
    http://rails.vandenabeele.com
    http://coderwall.com/peter_v

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  • Bob Smith at Feb 11, 2012 at 7:33 pm

    On Feb 9, 3:52 am, Peter Vandenabeele wrote:
    On Thu, Feb 9, 2012 at 7:07 AM, Hassan Schroeder <hassan.schroe...@gmail.com
    wrote:
    On Wed, Feb 8, 2012 at 8:54 PM, Bob Smith wrote:

    What I am trying to do is have a *unique value* set in each new record
    See:http://rubygems.org/gems/uuid
    Indeed.

    And maybe better to not mess with the `def initialize`, but use the
    `after_initialize` function that is provided by Rails. I did it like this.

    ../lib/uuid_helper.rb

    require 'uuidtools'

    module UUIDHelper
    extend ActiveSupport::Concern

    included do
    after_initialize :set_uuid
    def set_uuid
    unless uuid  # Note 1 below
    self.uuid = UUIDTools::UUID.random_create.to_s
    end
    end
    end
    end

    ../app/model/person.rb

    class Person < ActiveRecord::Base

    # UUID
    include UUIDHelper
    ...
    end

    Note 1:
    Be careful, it is a little tricky to _only_ set the value of the uuid
    when it is not yet present, otherwise reading back the value
    from the database will build a new instance of Person with a
    new random uuid. The code above is well tested and works.

    Maybe you will also need to add ../lib to your default load path.
    In config/application.rb

    # Custom directories with classes and modules you want to be
    autoloadable.
    config.autoload_paths += %W(#{config.root}/lib)
    config.autoload_paths += Dir["#{config.root}/lib/**/"]

    HTH,

    Peter

    *** Available for a new project ***

    Peter Vandenabeelehttp://twitter.com/peter_vhttp://rails.vandenabeele.comhttp://coderwall.com/peter_v
    I don't have a config/application.rb. Forgot to mention it, but I'm
    using 2.3.9 until I get rid of bugs, then the 3.0 project starts.. :>
    Can this be done for 2.3.9?


    Thanks
    Bob

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  • Bob Smith at Feb 26, 2012 at 9:33 pm

    On Feb 11, 2:33 pm, Bob Smith wrote:
    On Feb 9, 3:52 am, Peter Vandenabeele wrote:


    On Thu, Feb 9,2012at 7:07 AM, Hassan Schroeder <hassan.schroe...@gmail.com
    wrote:
    On Wed, Feb 8,2012at 8:54 PM, Bob Smith wrote:

    What I am trying to do is have a *unique value* set in each new record
    See:http://rubygems.org/gems/uuid
    Indeed.
    And maybe better to not mess with the `def initialize`, but use the
    `after_initialize` function that is provided by Rails. I did it like this.
    ../lib/uuid_helper.rb
    require 'uuidtools'
    module UUIDHelper
    extend ActiveSupport::Concern
    included do
    after_initialize :set_uuid
    def set_uuid
    unless uuid  # Note 1 below
    self.uuid = UUIDTools::UUID.random_create.to_s
    end
    end
    end
    end
    ../app/model/person.rb
    class Person < ActiveRecord::Base
    # UUID
    include UUIDHelper
    ...
    end
    Note 1:
    Be careful, it is a little tricky to _only_ set the value of the uuid
    when it is not yet present, otherwise reading back the value
    from the database will build a new instance of Person with a
    new random uuid. The code above is well tested and works.
    Maybe you will also need to add ../lib to your default load path.
    In config/application.rb
    # Custom directories with classes and modules you want to be
    autoloadable.
    config.autoload_paths += %W(#{config.root}/lib)
    config.autoload_paths += Dir["#{config.root}/lib/**/"]
    HTH,
    Peter
    *** Available for a new project ***
    Peter Vandenabeelehttp://twitter.com/peter_vhttp://rails.vandenabeele.comhttp://coderwa...
    I don't have a config/application.rb. Forgot to mention it, but I'm
    using 2.3.9 until I get rid of bugs, then the 3.0 project starts.. :>
    Can this be done for 2.3.9?

    Thanks
    Bob
    Finally found it. Here it is for anyone else in similar trouble.

    In the view

    <%= link_to_remote "Add a Person", :url => "/people/add_person" %>

    In the controller

    def add_person
    person = Person.new()
    person.hoh = $hoh
    $hoh = $hoh - 1
    render :update do |page|
    page.insert_html :bottom, 'empty', :partial => 'shared/
    person', :object => person
    end
    end

    This will add a new object AND allow the play with the hoh in the new
    model AND decrement it for the next new object.
    As usual, everything is possible in Rails, once you find an allowed
    way to do it,

    Bob <bsm2th@gmail.com>

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  • Michael Pavling at Feb 26, 2012 at 9:52 pm

    On 26 February 2012 21:32, Bob Smith wrote:
    Finally found it. Here it is for anyone else in similar trouble.

    def add_person
    person = Person.new()
    person.hoh = $hoh
    $hoh = $hoh - 1
    render :update do |page|
    page.insert_html :bottom, 'empty', :partial => 'shared/
    person', :object => person
    end
    end
    Global variables?
    For the love of all that's OO, at least hide it behind a singleton :-/
    *shakes head*

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  • Grentis at Feb 8, 2012 at 11:05 am
    You can use also after_initialize checking if the counter is already setted

    after_initialize :set_counter

    def set_counter
    self.counter ||= ModelName.all.count
    end

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  • Michael Pavling at Feb 8, 2012 at 11:12 am

    On 8 February 2012 11:05, grentis wrote:
    ModelName.all.count
    Please don't *ever* do this.
    If you want a count of all the objects in a table, use
    "ModeName.count". Using ".all.count" will instantiate an array of all
    of the objects just to do a count of the array... this could be very
    slow with a big table.

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  • Grentis at Feb 8, 2012 at 11:14 am
    Ops, sorry...I don't know why I add .all :(

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  • Valery Kvon at Feb 8, 2012 at 11:54 am

    On 08.02.2012, at 15:05, grentis wrote:

    You can use also after_initialize checking if the counter is already setted

    after_initialize :set_counter

    def set_counter
    self.counter ||= ModelName.all.count
    end
    Imagine 'create' action.

    During the period from the instance is initialized:
    @user = User.new(params[:user])
    to the moment it saved
    @user.save

    anyone else can create user object(s), so your @user will be saved with incorrect counter value.

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