阿雷爾AND子句和空狀態

Question

考慮下面的代碼片段：

def sql 
    billing_requests 
    .project(billing_requests[Arel.star]) 
    .where(
    filter_by_day 
     .and(filter_by_merchant) 
     .and(filter_by_operator_name) 
) 
    .to_sql 
end 

def filter_by_day 
    billing_requests[:created_at].gteq(@start_date).and(
    billing_requests[:created_at].lteq(@end_date) 
) 
end 

def filter_by_operator_name 
    unless @operator_name.blank? 
    return billing_requests[:operator_name].eq(@operator_name) 
    end 
end 

def filter_by_merchant 
    unless @merchant_id.blank? 
    return billing_requests[:merchant_id].eq(@merchant_id) 
    end 
end 

private 

def billing_requests 
    @table ||= Arel::Table.new(:billing_requests) 
end 

在方法時，商戶ID變空filter_by_merchant，應該是什麼，必須返回阿雷爾忽略AND子句效應的價值？ 另外，有沒有更好的方法來處理這種情況？

Answer 1

似乎不可能給and任何參數導致它什麼都不做。然而，你可以叫and條件：

def sql 
    billing_requests 
    .project(billing_requests[Arel.star]) 
    .where(filter_by_day_and_merchant_and_operator_name) 
    .to_sql 
end 

def filter_by_day 
    billing_requests[:created_at].gteq(@start_date).and(
    billing_requests[:created_at].lteq(@end_date) 
) 
end 

def filter_by_merchant 
    billing_requests[:merchant_id].eq(@merchant_id) 
end 

def filter_by_operator_name 
    billing_requests[:operator_name].eq(@operator_name) 
end 

def filter_by_day_and_merchant 
    if @merchant_id.blank? 
    filter_by_day 
    else 
    filter_by_day.and(filter_by_merchant) 
    end 
end 

def filter_by_day_and_merchant_and_operator_name 
    if @operator_name.blank? 
    filter_by_day_and_merchant 
    else 
    filter_by_day_and_merchant.and(filter_by_operator_name) 
    end 
end 

private 

def billing_requests 
    @table ||= Arel::Table.new(:billing_requests) 
end 

這是非常笨拙，但它能夠完成任務。

Answer 2

您應該返回true。當你運行.and（true）時，它最終會在sql中轉換爲'AND 1'。

def filter_by_merchant 
    return true if @merchant_id.blank? 

    billing_requests[:merchant_id].eq(@merchant_id) 
end 

Answer 3

def sql 
    billing_requests 
    .project(billing_requests[Arel.star]) 
    .where(conditions) 
    .to_sql 
end 

def conditions 
    ret = filter_by_day 
    ret = ret.and(filter_by_merchant) unless @merchant_id.blank? 
    ret = ret.and(filter_by_operator_name) unless @operator_name.blank? 
    ret 
end 

def filter_by_day 
    billing_requests[:created_at].gteq(@start_date).and(
    billing_requests[:created_at].lteq(@end_date) 
) 
end 

def filter_by_operator_name 
    billing_requests[:operator_name].eq(@operator_name) 
end 

def filter_by_merchant 
    billing_requests[:merchant_id].eq(@merchant_id) 
end 

private 

def billing_requests 
    @table ||= Arel::Table.new(:billing_requests) 
end