導軌 - 準備好的語句

Question

建設條件陣列我試圖建立一個條件陣列使用在一份聲明是：

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

我試着做以下，但得到「的ActiveRecord ::的錯誤PreparedStatementInvalid（錯號碼綁定變量（4 2）「：

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

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

什麼是建設一個條件準備語句的正確方法

Answer 1

的問題是，你是BUIL因爲你將所有的參數都傳遞給了問題標記。

你得到的查詢看起來是這樣的：

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

爲了達到你想要的數組，你會做這樣的事情。

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

如果你重複上一步，你應該得到你需要的結果。

Answer 2

您可能會發現這更容易做的一個哈希：

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

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