自定义网格在WPF网格中调整大小(Custom grid resize in WPF grid)

 attr_accessor和attr_accessible ，尽管几乎完全相同的拼写，但绝对是不同的方法。 
 
 attr_accessor ，一个本机Ruby方法，它为类的实例定义一个getter和一个setter方法： 
 
class User
  attr_accessor :password
end

u = User.new
u.password = "secret"
u.password # => "secret"
 
 attr_accessible是Rails带来的一种方法，它的意思是将模型的已有属性“列入白名单”。 attr_accessible中枚举的属性可以稍后通过模型属性的质量分配进行更改（而其他属性将被列入黑名单且不可更改）： 
 
class Account < ActiveRecord::Base
  # First, you define 2 attributes: "password" and "created_at"
  attr_accessor :password
  attr_accessor :created_at

  # Now you say that you want "password" attribute
  # to be changeable via mass-assignment, while making
  # "created_at" to be non-changeable via mass-assignment
  attr_accessible :password
end

a = Account.new

# Perform mass-assignment (which is usually done when you update
# your model using the attributes submitted via a web form)
a.update_attributes(:password => "secret", :created_at => Time.now)

a.password # => "secret"
# "password" is changed

a.created_at # => nil
# "created_at" remains not changed
 
 您可以使用attr_accessible来防止“外人”干扰模型的某些属性（例如，您不希望您的“Account.superadmin”属性可以通过简单的表单提交进行更改，这将是一个糟糕的安全问题）。 
 
 请注意，您可以单独更改属性，无论其“白名单/黑名单”状态如何： 
 
a.created_at = Time.now

a.created_at # => 2012-09-16 10:03:14

attr_accessor and attr_accessible, despite almost identical spelling, are absolutely different methods.
 
attr_accessor, a native Ruby method which defines a getter and a setter method for the instance of the class:
 
class User
  attr_accessor :password
end

u = User.new
u.password = "secret"
u.password # => "secret"
 
attr_accessible is a method brought by Rails and it is meant to "whitelist" already existing attributes of a model. Attributes enumerated in attr_accessible can be later changed via mass-assignment of model attributes (while other attributes will be blacklisted and not changeable):
 
class Account < ActiveRecord::Base
  # First, you define 2 attributes: "password" and "created_at"
  attr_accessor :password
  attr_accessor :created_at

  # Now you say that you want "password" attribute
  # to be changeable via mass-assignment, while making
  # "created_at" to be non-changeable via mass-assignment
  attr_accessible :password
end

a = Account.new

# Perform mass-assignment (which is usually done when you update
# your model using the attributes submitted via a web form)
a.update_attributes(:password => "secret", :created_at => Time.now)

a.password # => "secret"
# "password" is changed

a.created_at # => nil
# "created_at" remains not changed
 
You use attr_accessible to prevent meddling with some attributes of your models by "outsiders" (e.g. you wouldn't want your "Account.superadmin" attribute to be changeable via a simple form submission, which would be a bad security issue).
 
Note, that you can change the attributes individually, regardless of their "whitelisting/blacklisting" status:
 
a.created_at = Time.now

a.created_at # => 2012-09-16 10:03:14