Class: NilClass

### Home Classes Methods

### In Files

- lib/active_support/core_ext/object/blank.rb
- lib/active_support/core_ext/object/duplicable.rb
- lib/active_support/core_ext/object/to_param.rb
- lib/active_support/core_ext/object/try.rb
- lib/active_support/json/encoding.rb
- lib/active_support/whiny_nil.rb

### Parent

Object

### Methods

- ::add_whiner
- #as_json
- #blank?
- #duplicable?
- #encode_json
- #id
- #to_param
- #try

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No matching classes.

# NilClass

Extensions to `nil` which allow for more helpful error messages for people who are new to Rails.

NilClass#id exists in Ruby 1.8 (though it is deprecated). Since `id` is a fundamental method of Active Record models NilClass#id is redefined as well to raise a RuntimeError and warn the user. She probably wanted a model database identifier and the 4 returned by the original method could result in obscure bugs.

The flag `config.whiny_nils` determines whether this feature is enabled. By default it is on in development and test modes, and it is off in production mode.

### Public Class Methods

add_whiner(klass) click to toggle source

    # File lib/active_support/whiny_nil.rb, line 15
    def self.add_whiner(klass)
      ActiveSupport::Deprecation.warn "NilClass.add_whiner is deprecated and this functionality is "        "removed from Rails versions as it affects Ruby 1.9 performance.", caller
    end

### Public Instance Methods

as_json(options = nil) click to toggle source

    # File lib/active_support/json/encoding.rb, line 171
    def as_json(options = nil) self end

blank?() click to toggle source

`nil` is blank:

    nil.blank? # => true

    # File lib/active_support/core_ext/object/blank.rb, line 47
    def blank?
      true
    end

duplicable?() click to toggle source

`nil` is not duplicable:

    nil.duplicable? # => false
    nil.dup         # => TypeError: can't dup NilClass

    # File lib/active_support/core_ext/object/duplicable.rb, line 35
    def duplicable?
      false
    end

encode_json(encoder) click to toggle source

    # File lib/active_support/json/encoding.rb, line 172
    def encode_json(encoder) 'null' end

id() click to toggle source

Raises a RuntimeError when you attempt to call `id` on `nil`.

    # File lib/active_support/whiny_nil.rb, line 21
    def id
      raise RuntimeError, "Called id for nil, which would mistakenly be #{object_id} -- if you really wanted the id of nil, use object_id", caller
    end

to_param() click to toggle source

    # File lib/active_support/core_ext/object/to_param.rb, line 9
    def to_param
      self
    end

try(*args) click to toggle source

Calling `try` on `nil` always returns `nil`. It becomes specially helpful when navigating through associations that may return `nil`.

### Examples

    nil.try(:name) # => nil

Without `try`

    @person && !@person.children.blank? && @person.children.first.name

With `try`

    @person.try(:children).try(:first).try(:name)

    # File lib/active_support/core_ext/object/try.rb, line 54
    def try(*args)
      nil
    end

[Validate]

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