Rails - 准备语句的构建条件数组

Question

我正在尝试构建一个条件数组以在预准备语句中使用：

Cars.find(:all, :conditions=>["color = ? AND doors = ? AND type = ?", "black", "4", "sedan"])

我已尝试执行以下操作但收到错误“ActiveRecord :: PreparedStatementInvalid（错误的绑定变量数量（4 for for 2）”）：

conditions = []
conditions += ["color = ?", "black"]
conditions += ["doors = ?", "4"]
conditions += ["type = ?", "sedan"]

Cars.find(:all, :conditions=>conditions)

为准备好的陈述构建条件的正确方法是什么？

Answer 1

问题是你正在构建一个错误的查询，因为你通过语句将params传递给了问号。

您生成的查询看起来像这样：

 => ["color = ?", "black", "doors = ?", "4", "type = ?", "sedan"] 

为了实现你想要的阵列，你必须做这样的事情。

conditions = []
conditions += ["color = ?", "black"]
array = ["doors = ?", "4"]
conditions[0].concat(" AND ")
conditions[0].concat(array[0])
conditions << array[1]

如果您重复最后一步，则应获得所需的结果。

Answer 2

您可能会发现使用哈希更容易：

conditions = {}
conditions[:color] = "black"
conditions[:doors] = 4
conditions[:type] = "sedan"

Cars.find(:all, :conditions=>conditions)