小编Dam*_*ien的帖子

隐式展开Bool类型似乎不起作用:

var aBoolean: Bool!    // nil
aBoolean = false       // false
aBoolean               // false

aBoolean == true       // false
aBoolean == false      // true

if aBoolean {
    "Hum..."            // "Hum..."
} else {
    "Normal"
}

if aBoolean! {
    "Hum..."
} else {
    "Normal"          // "Normal"
}

如果我已经宣布了aBoolean这样的话var aBoolean: Bool?,这将是预期的行为,但在这里,我不明白.

这是正确的行为吗？我没有找到任何关于它的文档.

谢谢!

举一个每个人都熟悉的例子,想想StackOverflow.用户has_many :questions,has_many :answers和她的问题和答案,可以评论.(评论是多态的).

我希望通过对该用户的问题或答案的评论来获得针对特定用户的所有回复:

class User < ActiveRecord::Base
  has_many :questions
  has_many :answers
  has_many :comments
  has_many :responses, through: [:questions, :answers], source: :comments
end

class Question < ActiveRecord::Base
  belongs_to :user
  has_many :answers
  has_many :comments, as: :commentable
end

class Answer < ActiveRecord::Base
  belongs_to :user
  belongs_to :question
  has_many :comments, as: :commentable
end

class Comment < ActiveRecord::Base
  belongs_to :commentable, polymorphic: true
end

当然,has_many :responses, through: [:questions, :answers], source: :comments不起作用.

是否有Rails方法可以做到这一点？

谢谢.

如何从函数返回一个可变数组？

这是一段简短的代码片段,使其更加清晰:

var tasks = ["Mow the lawn", "Call Mom"]
var completedTasks = ["Bake a cake"]

func arrayAtIndex(index: Int) -> String[] {
    if index == 0 {
        return tasks
    } else {
        return completedTasks
    }
}

arrayAtIndex(0).removeAtIndex(0)
// Immutable value of type 'String[]' only has mutating members named 'removeAtIndex'

以下片段有效,但我必须返回一个Array,而不是一个NSMutableArray

var tasks: NSMutableArray = ["Mow the lawn", "Call Mom"]
var completedTasks: NSMutableArray = ["Bake a cake"]

func arrayAtIndex(index: Int) -> NSMutableArray {
    if index == 0 { …

Rails 3.1,Ruby 1.9.3

所以我有两个模型,都有两组坐标.

第一种模式,Load具有from_lat/lng,以及to_lat/lng.
第二个型号,卡车,current_lat/lng以及destination_lat/lng.

我要做的是找到所有结果,current_lat/lng或者destination_lat/lng来自Load模型的to_lat/lng附近的Truck模型.

我的车道模型是这样的:

class Load < ActiveRecord::Base  

  has_many :trucks

  geocoded_by :custom_geocode  

  after_validation :custom_geocode

  def custom_geocode  
    var = Geocoder.coordinates([from_city,from_state].compact.join(','))  
    var2 = Geocoder.coordinates([to_city,to_state].compact.join(','))  
    self.from_lat = var.first  
    self.from_lng = var.last  
    self.to_lat = var2.first  
    self.to_lng = var2.last  
  end
end

在我看来,我有:

<% for truck in @trucks %>  
  <li><%= truck.destination_lat %></li>  
<% end %>

目前我在load_controller中使用它:

def show
  @load = Load.find(params[:id])
  @trucks = Truck.near([@load.from_lat, @load.from_lng], 100, :order => …