Question

我想知道如何根据params是否存在来成功设置动态Active Record查询。

我有这个查询

Animal.joins(:user).where(animal_type: params[:animal_type], rehomed: params[:rehomed], users: {town: params[:animal_town]})

我已经尝试了这些方面的东西，但我的语法都错了，我相信：

conditions = []
conditions << [ animal_type: params[:animal_type], ] if params[:animal_type].present?
conditions << [ rehomed: params[:rehomed], ] if params[:rehomed].present?
conditions << [ users: {town: params[:animal_town]} ] if params[:animal_town].present?
@animals = Animal.joins(:user).where(conditions)

我不想把它全部放在嵌套的哈希中，是吗？

Answer 1

你必须这样做：

conditions = {}
conditions.merge!(animal_type: params[:animal_type]) if params[:animal_type].present?
conditions.merge!(rehomed: params[:rehomed]) if params[:rehomed].present?
conditions.merge!(users: {town: params[:animal_town]}) if params[:animal_town].present?

@animals = Animal.joins(:user).where(conditions)

Answer 2

我会做这样的事情：

scope = Animal.joins(:user)
scope = scope.where(animal_type: params[:animal_type])     if params[:animal_type].present?
scope = scope.where(rehomed: params[:rehomed])             if params[:rehomed].present?
scope = scope.where(users: { town: params[:animal_town] }) if params[:animal_town].present?

@animals = scope

进一步改进：将范围的构建移动到Animal模型中的方法：

# in controller
@animals = Animal.find_by_query(params.slice(:animal_type, :rehomed, :animal_town))

# in Animal model
def self.find_by_query(query = {})
  query.reject { |_, v| v.blank? }

  scope = joins(:user)
  scope = scope.where(animal_type: query[:animal_type])     if query[:animal_type]
  scope = scope.where(rehomed: query[:rehomed])             if query[:rehomed]
  scope = scope.where(users: { town: query[:animal_town] }) if query[:animal_town]
  scope
end

在Rails中构建动态ActiveRecord查询

2 个答案: