定義變量

Question

當我一個Rails應用程序的頁面上定義了三個變量簡化紅寶石控制流程：

if current_user 
    if Vote.where(:user_id => current_user.id, :post_id => post.id, :direction => 0).count > 0 
     active = ' upactive' 
    elsif Vote.where(:user_id => current_user.id, :post_id => post.id, :direction => 1).count > 0 
     active = ' downactive' 
    end 
    end 

    unless Vote.group(:post_id).where(:post_id => @posts.map(&:id), :direction => 0).count[post.id] == nil 
    upvotes = Vote.group(:post_id).where(:post_id => @posts.map(&:id), :direction => 0).count[post.id] 
    else 
    upvotes = 0 
    end 

    unless Vote.group(:post_id).where(:post_id => @posts.map(&:id), :direction => 1).count[post.id] == nil 
    downvotes = Vote.group(:post_id).where(:post_id => @posts.map(&:id), :direction => 1).count[post.id] 
    else 
    downvotes = 0 
    end 

我注意到有相當多的在if和unless語句重複的代碼。我怎樣才能寫出三個與上述變量相同的變量聲明，確保變量始終爲0而不是nil。

Answer 1

您可以在此使用條件賦值運算符來幫助減少代碼。例如：

if current_user 
    if Vote.where(:user_id => current_user.id, :post_id => post.id, :direction => 0).count > 0 
    active = ' upactive' 
    elsif Vote.where(:user_id => current_user.id, :post_id => post.id, :direction => 1).count > 0 
    active = ' downactive' 
    end 
end 

upvotes = Vote.group(:post_id).where(:post_id => @posts.map(&:id), :direction => 0).count[post.id] || 0 
downvotes = Vote.group(:post_id).where(:post_id => @posts.map(&:id), :direction => 1).count[post.id] || 0 

如果所述第一部分的計算結果爲零，則使用右側作爲缺省值的有條件分配操作者基本上說。