rails 多对多关系多表查询

发表于:，更新于:，By Sally
大纲
  1. 1. model的关系
  2. 2. 查询某一个supervisor的所有decoartingcases

model的关系

  • Decoratingcase
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has_many :supervisor_operations
has_many :supervisors, :through => :supervisor_operations
  • Supervisor
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has_many :supervisor_operations
has_many :decoratingcases, :through => :supervisor_operations
  • SupervisorOperation
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belongs_to :decoratingcase
belongs_to :supervisor

查询某一个supervisor的所有decoartingcases

  • 先查处所有的supervisor_operations
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supervisor_operations = SupervisorOperation.where(:supervisor_id => params[:supervisor_id])
  • 再查处对应supervisor的decoratingcase_id

返回的是一个数组，包含所有decoratingcase_id，eg：[11, 26, 26, 27, 11, 28, 29, 11, 27, 27, 11, 30, 31, 32, 33, 49, 50]

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decoartingcase_ids = supervisor_operations.map(&:decoratingcase_id)
  • 获得所有的decoratingcases
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Decoratingcase.where(id:decoratingcase_ids)
  • 连接起来的写法
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supervisor_decorating = SupervisorOperation.where(:supervisor_id => params[:supervisor_id])
@decoratingcases = Decoratingcase.where(id:supervisor_decorating.map(&:decoratingcase_id))