has_one association through has_many with dynamic conditions

has_one association through has_many with dynamic conditions - Rails

I have three tables:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group
end

class AssignmentsGroup
 has_many :assignments
 validate :uniqueness_of_keeper
end

Assignments associated with a single assignment_group must have a single keeper. My question is: how can I add a has_one: keeper association to AssignmentsGroup given that all associated assignments will have the same keeper?

edited Nov 16 '18 at 3:16

asked Nov 16 '18 at 1:16

dn1985

add a comment |

I have three tables:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group
end

class AssignmentsGroup
 has_many :assignments
 validate :uniqueness_of_keeper
end

edited Nov 16 '18 at 3:16

asked Nov 16 '18 at 1:16

dn1985

add a comment |

I have three tables:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group
end

class AssignmentsGroup
 has_many :assignments
 validate :uniqueness_of_keeper
end

edited Nov 16 '18 at 3:16

asked Nov 16 '18 at 1:16

dn1985

I have three tables:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group
end

class AssignmentsGroup
 has_many :assignments
 validate :uniqueness_of_keeper
end

ruby-on-rails activerecord associations

edited Nov 16 '18 at 3:16

asked Nov 16 '18 at 1:16

dn1985

edited Nov 16 '18 at 3:16

asked Nov 16 '18 at 1:16

dn1985

edited Nov 16 '18 at 3:16

asked Nov 16 '18 at 1:16

dn1985

asked Nov 16 '18 at 1:16

dn1985

asked Nov 16 '18 at 1:16

dn1985

add a comment |

1 Answer
1

active

oldest

votes

Sorry if I've misunderstood your problem as it's not clear what the association to between AssignmentGroup and Assignment should be, but try this:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group # will need to add a reference to the assignments table
end

class AssignmentsGroup
 has_many :assignments
 has_many :keepers, through: assignments
 validate :single_keeper

 private 

 def single_keeper
 errors.add(:base, "can only have one keeper") unless keepers.uniq.length == 1
 end
end

See https://guides.rubyonrails.org/active_record_validations.html#custom-methods

edited Nov 16 '18 at 3:57

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

whoops, forgot to add the belongs_to. Yes, Assignment belongs_to :assignment_group. My question is how can I add has_one :keeper to AssignmentGroup

– dn1985
Nov 16 '18 at 3:18

@dn1985 you can't cause there are many keepers if AssignmentsGroup has_many :assignments. But with a validation rule you should be able to add that constraint, which is what I tried to show above in single_keeper validation.

– Simon L. Brazell
Nov 16 '18 at 3:38

add a comment |

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1 Answer
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active

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1 Answer
1

active

oldest

votes

Sorry if I've misunderstood your problem as it's not clear what the association to between AssignmentGroup and Assignment should be, but try this:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group # will need to add a reference to the assignments table
end

class AssignmentsGroup
 has_many :assignments
 has_many :keepers, through: assignments
 validate :single_keeper

 private 

 def single_keeper
 errors.add(:base, "can only have one keeper") unless keepers.uniq.length == 1
 end
end

See https://guides.rubyonrails.org/active_record_validations.html#custom-methods

edited Nov 16 '18 at 3:57

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

whoops, forgot to add the belongs_to. Yes, Assignment belongs_to :assignment_group. My question is how can I add has_one :keeper to AssignmentGroup

– dn1985
Nov 16 '18 at 3:18

@dn1985 you can't cause there are many keepers if AssignmentsGroup has_many :assignments. But with a validation rule you should be able to add that constraint, which is what I tried to show above in single_keeper validation.

– Simon L. Brazell
Nov 16 '18 at 3:38

add a comment |

Sorry if I've misunderstood your problem as it's not clear what the association to between AssignmentGroup and Assignment should be, but try this:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group # will need to add a reference to the assignments table
end

class AssignmentsGroup
 has_many :assignments
 has_many :keepers, through: assignments
 validate :single_keeper

 private 

 def single_keeper
 errors.add(:base, "can only have one keeper") unless keepers.uniq.length == 1
 end
end

See https://guides.rubyonrails.org/active_record_validations.html#custom-methods

edited Nov 16 '18 at 3:57

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

whoops, forgot to add the belongs_to. Yes, Assignment belongs_to :assignment_group. My question is how can I add has_one :keeper to AssignmentGroup

– dn1985
Nov 16 '18 at 3:18

@dn1985 you can't cause there are many keepers if AssignmentsGroup has_many :assignments. But with a validation rule you should be able to add that constraint, which is what I tried to show above in single_keeper validation.

– Simon L. Brazell
Nov 16 '18 at 3:38

add a comment |

Sorry if I've misunderstood your problem as it's not clear what the association to between AssignmentGroup and Assignment should be, but try this:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group # will need to add a reference to the assignments table
end

class AssignmentsGroup
 has_many :assignments
 has_many :keepers, through: assignments
 validate :single_keeper

 private 

 def single_keeper
 errors.add(:base, "can only have one keeper") unless keepers.uniq.length == 1
 end
end

See https://guides.rubyonrails.org/active_record_validations.html#custom-methods

edited Nov 16 '18 at 3:57

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

Sorry if I've misunderstood your problem as it's not clear what the association to between AssignmentGroup and Assignment should be, but try this:

class Keeper
 has_many :assignments
end

class Assignment
 belongs_to :keeper
 belongs_to :assignment_group # will need to add a reference to the assignments table
end

class AssignmentsGroup
 has_many :assignments
 has_many :keepers, through: assignments
 validate :single_keeper

 private 

 def single_keeper
 errors.add(:base, "can only have one keeper") unless keepers.uniq.length == 1
 end
end

See https://guides.rubyonrails.org/active_record_validations.html#custom-methods

edited Nov 16 '18 at 3:57

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

edited Nov 16 '18 at 3:57

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

answered Nov 16 '18 at 2:39

Simon L. Brazell

51639

whoops, forgot to add the belongs_to. Yes, Assignment belongs_to :assignment_group. My question is how can I add has_one :keeper to AssignmentGroup

– dn1985
Nov 16 '18 at 3:18

@dn1985 you can't cause there are many keepers if AssignmentsGroup has_many :assignments. But with a validation rule you should be able to add that constraint, which is what I tried to show above in single_keeper validation.

– Simon L. Brazell
Nov 16 '18 at 3:38

add a comment |

whoops, forgot to add the belongs_to. Yes, Assignment belongs_to :assignment_group. My question is how can I add has_one :keeper to AssignmentGroup

– dn1985
Nov 16 '18 at 3:18

@dn1985 you can't cause there are many keepers if AssignmentsGroup has_many :assignments. But with a validation rule you should be able to add that constraint, which is what I tried to show above in single_keeper validation.

– Simon L. Brazell
Nov 16 '18 at 3:38

whoops, forgot to add the belongs_to. Yes, Assignment belongs_to :assignment_group. My question is how can I add has_one :keeper to AssignmentGroup

– dn1985
Nov 16 '18 at 3:18

@dn1985 you can't cause there are many keepers if AssignmentsGroup has_many :assignments. But with a validation rule you should be able to add that constraint, which is what I tried to show above in single_keeper validation.

– Simon L. Brazell
Nov 16 '18 at 3:38

add a comment |

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