abstract class Class

Casts other to this class.

This is the same as using as, but allows the class to be passed around as an argument. See the documentation on as for more information.

klass = Int32
number = [99, "str"][0]
typeof(number)             # => (String | Int32)
typeof(klass.cast(number)) # => Int32

Deserializes the given JSON in string_or_io into an instance of self, assuming the JSON consists of an JSON object with key root, and whose value is the value to deserialize.

Int32.from_json(%({"main": 1}), root: "main") # => 1

Deserializes the given JSON in string_or_io into an instance of self. This simply creates a parser = JSON::PullParser and invokes new(parser): classes that want to provide JSON deserialization must provide an def initialize(parser : JSON::PullParser method.

Int32.from_json("1")                # => 1
Array(Int32).from_json("[1, 2, 3]") # => [1, 2, 3]

Returns the name of this class.

String.name # => "String"

Returns true if this class is Nil.

Int32.nilable? # => false
Nil.nilable?   # => true

Returns the union type of self and other.

Int32 | Char # => (Int32 | Char)

Casts other to this class.

This is the same as using as, but allows the class to be passed around as an argument. See the documentation on as for more information.

klass = Int32
number = [99, "str"][0]
typeof(number)             # => (String | Int32)
typeof(klass.cast(number)) # => Int32

Deserializes the given JSON in string_or_io into an instance of self, assuming the JSON consists of an JSON object with key root, and whose value is the value to deserialize.

Int32.from_json(%({"main": 1}), root: "main") # => 1

Deserializes the given JSON in string_or_io into an instance of self. This simply creates a parser = JSON::PullParser and invokes new(parser): classes that want to provide JSON deserialization must provide an def initialize(parser : JSON::PullParser method.

Int32.from_json("1")                # => 1
Array(Int32).from_json("[1, 2, 3]") # => [1, 2, 3]

Returns the name of this class.

String.name # => "String"

Returns true if this class is Nil.

Int32.nilable? # => false
Nil.nilable?   # => true

Returns the union type of self and other.

Int32 | Char # => (Int32 | Char)

Defines getter methods for each of the given arguments.

Writing:

class Person
  class_getter name
end

Is the same as writing:

class Person
  def self.name
    @@name
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_getter :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  class_getter name : String
end

Is the same as writing:

class Person
  @@name : String

  def self.name : String
    @@name
  end
end

The type declaration can also include an initial value:

class Person
  class_getter name : String = "John Doe"
end

Is the same as writing:

class Person
  @@name : String = "John Doe"

  def self.name : String
    @@name
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  class_getter name = "John Doe"
end

Is the same as writing:

class Person
  @@name = "John Doe"

  def self.name : String
    @@name
  end
end

If a block is given to the macro, a getter is generated with a variable that is lazily initialized with the block's contents:

class Person
  class_getter(birth_date) { Time.now }
end

Is the same as writing:

class Person
  def self.birth_date
    @@birth_date ||= Time.now
  end
end

Defines raise-on-nil and nilable getter methods for each of the given arguments.

Writing:

class Person
  class_getter! name
end

Is the same as writing:

class Person
  def self.name?
    @@name
  end

  def self.name
    @@name.not_nil!
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_getter! :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type, as nilable.

class Person
  class_getter! name : String
end

is the same as writing:

class Person
  @@name : String?

  def self.name?
    @@name
  end

  def self.name
    @@name.not_nil!
  end
end

Defines query getter methods for each of the given arguments.

Writing:

class Person
  class_getter? happy
end

Is the same as writing:

class Person
  def self.happy?
    @@happy
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_getter? :happy, "famous"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  class_getter? happy : Bool
end

is the same as writing:

class Person
  @@happy : Bool

  def self.happy? : Bool
    @@happy
  end
end

The type declaration can also include an initial value:

class Person
  class_getter? happy : Bool = true
end

Is the same as writing:

class Person
  @@happy : Bool = true

  def self.happy? : Bool
    @@happy
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  class_getter? happy = true
end

Is the same as writing:

class Person
  @@happy = true

  def self.happy?
    @@happy
  end
end

Defines property methods for each of the given arguments.

Writing:

class Person
  class_property name
end

Is the same as writing:

class Person
  def self.name=(@@name)
  end

  def self.name
    @@name
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_property :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  class_property name : String
end

Is the same as writing:

class Person
  @@name : String

  def self.name=(@@name)
  end

  def self.name
    @@name
  end
end

The type declaration can also include an initial value:

class Person
  class_property name : String = "John Doe"
end

Is the same as writing:

class Person
  @@name : String = "John Doe"

  def self.name=(@@name : String)
  end

  def self.name
    @@name
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  class_property name = "John Doe"
end

Is the same as writing:

class Person
  @@name = "John Doe"

  def self.name=(@@name : String)
  end

  def self.name
    @@name
  end
end

If a block is given to the macro, a property is generated with a variable that is lazily initialized with the block's contents:

class Person
  class_property(birth_date) { Time.now }
end

Is the same as writing:

class Person
  def self.birth_date
    @@birth_date ||= Time.now
  end

  def self.birth_date=(@@birth_date)
  end
end

Defines raise-on-nil property methods for each of the given arguments.

Writing:

class Person
  class_property! name
end

Is the same as writing:

class Person
  def self.name=(@@name)
  end

  def self.name?
    @@name
  end

  def self.name
    @@name.not_nil!
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_property! :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type, as nilable.

class Person
  class_property! name : String
end

Is the same as writing:

class Person
  @@name : String?

  def self.name=(@@name)
  end

  def self.name?
    @@name
  end

  def self.name
    @@name.not_nil!
  end
end

Defines query property methods for each of the given arguments.

Writing:

class Person
  class_property? happy
end

Is the same as writing:

class Person
  def self.happy=(@@happy)
  end

  def self.happy?
    @@happy
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_property? :happy, "famous"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  class_property? happy : Bool
end

Is the same as writing:

class Person
  @@happy : Bool

  def self.happy=(@@happy)
  end

  def self.happy?
    @@happy
  end

  def self.happy
    @@happy.not_nil!
  end
end

The type declaration can also include an initial value:

class Person
  class_property? happy : Bool = true
end

Is the same as writing:

class Person
  @@happy : Bool = true

  def self.happy=(@@happy : Bool)
  end

  def self.happy? : Bool
    @@happy
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  class_property? happy = true
end

Is the same as writing:

class Person
  @@happy = true

  def self.happy=(@@happy)
  end

  def self.happy?
    @@happy
  end
end

Defines setter methods for each of the given arguments.

Writing:

class Person
  class_setter name
end

Is the same as writing:

class Person
  def self.name=(@@name)
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  class_setter :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  class_setter name : String
end

is the same as writing:

class Person
  @@name : String

  def self.name=(@@name : String)
  end
end

The type declaration can also include an initial value:

class Person
  class_setter name : String = "John Doe"
end

Is the same as writing:

class Person
  @@name : String = "John Doe"

  def self.name=(@@name : String)
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  class_setter name = "John Doe"
end

Is the same as writing:

class Person
  @@name = "John Doe"

  def self.name=(@@name)
  end
end

Defines a #clone method that returns a copy of this object with all instance variables cloned (#clone is in turn invoked on them).

Defines an #== method by comparing the given fields.

The generated #== method has a self restriction.

class Person
  def initialize(@name, @age)
  end

  # Define a `==` method that compares @name and @age
  def_equals @name, @age
end

Defines #hash and #== method from the given fields.

The generated #== method has a self restriction.

class Person
  def initialize(@name, @age)
  end

  # Define a hash method based on @name and @age
  # Define a `==` method that compares @name and @age
  def_equals_and_hash @name, @age
end

Defines a #hash method computed from the given fields.

class Person
  def initialize(@name, @age)
  end

  # Define a hash method based on @name and @age
  def_hash @name, @age
end

Delegate methods to to.

Note that due to current language limitations this is only useful when no captured blocks are involved.

class StringWrapper
  def initialize(@string : String)
  end

  delegate downcase, to: @string
  delegate gsub, to: @string
  delegate empty?, capitalize, to: @string
end

wrapper = StringWrapper.new "HELLO"
wrapper.downcase       # => "hello"
wrapper.gsub(/E/, "A") # => "HALLO"
wrapper.empty?         # => false
wrapper.capitalize     # => "Hello"

Forwards missing methods to delegate.

class StringWrapper
  def initialize(@string : String)
  end

  forward_missing_to @string
end

wrapper = StringWrapper.new "HELLO"
wrapper.downcase       # => "hello"
wrapper.gsub(/E/, "A") # => "HALLO"

Defines getter methods for each of the given arguments.

Writing:

class Person
  getter name
end

Is the same as writing:

class Person
  def name
    @name
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  getter :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  getter name : String
end

Is the same as writing:

class Person
  @name : String

  def name : String
    @name
  end
end

The type declaration can also include an initial value:

class Person
  getter name : String = "John Doe"
end

Is the same as writing:

class Person
  @name : String = "John Doe"

  def name : String
    @name
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  getter name = "John Doe"
end

Is the same as writing:

class Person
  @name = "John Doe"

  def name : String
    @name
  end
end

If a block is given to the macro, a getter is generated with a variable that is lazily initialized with the block's contents:

class Person
  getter(birth_date) { Time.now }
end

Is the same as writing:

class Person
  def birth_date
    @birth_date ||= Time.now
  end
end

Defines raise-on-nil and nilable getter methods for each of the given arguments.

Writing:

class Person
  getter! name
end

Is the same as writing:

class Person
  def name?
    @name
  end

  def name
    @name.not_nil!
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  getter! :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type, as nilable.

class Person
  getter! name : String
end

is the same as writing:

class Person
  @name : String?

  def name?
    @name
  end

  def name
    @name.not_nil!
  end
end

Defines query getter methods for each of the given arguments.

Writing:

class Person
  getter? happy
end

Is the same as writing:

class Person
  def happy?
    @happy
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  getter? :happy, "famous"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  getter? happy : Bool
end

is the same as writing:

class Person
  @happy : Bool

  def happy? : Bool
    @happy
  end
end

The type declaration can also include an initial value:

class Person
  getter? happy : Bool = true
end

Is the same as writing:

class Person
  @happy : Bool = true

  def happy? : Bool
    @happy
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  getter? happy = true
end

Is the same as writing:

class Person
  @happy = true

  def happy?
    @happy
  end
end

Defines property methods for each of the given arguments.

Writing:

class Person
  property name
end

Is the same as writing:

class Person
  def name=(@name)
  end

  def name
    @name
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  property :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  property name : String
end

Is the same as writing:

class Person
  @name : String

  def name=(@name)
  end

  def name
    @name
  end
end

The type declaration can also include an initial value:

class Person
  property name : String = "John Doe"
end

Is the same as writing:

class Person
  @name : String = "John Doe"

  def name=(@name : String)
  end

  def name
    @name
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  property name = "John Doe"
end

Is the same as writing:

class Person
  @name = "John Doe"

  def name=(@name : String)
  end

  def name
    @name
  end
end

If a block is given to the macro, a property is generated with a variable that is lazily initialized with the block's contents:

class Person
  property(birth_date) { Time.now }
end

Is the same as writing:

class Person
  def birth_date
    @birth_date ||= Time.now
  end

  def birth_date=(@birth_date)
  end
end

Defines raise-on-nil property methods for each of the given arguments.

Writing:

class Person
  property! name
end

Is the same as writing:

class Person
  def name=(@name)
  end

  def name?
    @name
  end

  def name
    @name.not_nil!
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  property! :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type, as nilable.

class Person
  property! name : String
end

Is the same as writing:

class Person
  @name : String?

  def name=(@name)
  end

  def name?
    @name
  end

  def name
    @name.not_nil!
  end
end

Defines query property methods for each of the given arguments.

Writing:

class Person
  property? happy
end

Is the same as writing:

class Person
  def happy=(@happy)
  end

  def happy?
    @happy
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  property? :happy, "famous"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  property? happy : Bool
end

Is the same as writing:

class Person
  @happy : Bool

  def happy=(@happy)
  end

  def happy?
    @happy
  end

  def happy
    @happy.not_nil!
  end
end

The type declaration can also include an initial value:

class Person
  property? happy : Bool = true
end

Is the same as writing:

class Person
  @happy : Bool = true

  def happy=(@happy : Bool)
  end

  def happy? : Bool
    @happy
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  property? happy = true
end

Is the same as writing:

class Person
  @happy = true

  def happy=(@happy)
  end

  def happy?
    @happy
  end
end

Defines setter methods for each of the given arguments.

Writing:

class Person
  setter name
end

Is the same as writing:

class Person
  def name=(@name)
  end
end

The arguments can be string literals, symbol literals or plain names:

class Person
  setter :name, "age"
end

If a type declaration is given, a variable with that name is declared with that type.

class Person
  setter name : String
end

is the same as writing:

class Person
  @name : String

  def name=(@name : String)
  end
end

The type declaration can also include an initial value:

class Person
  setter name : String = "John Doe"
end

Is the same as writing:

class Person
  @name : String = "John Doe"

  def name=(@name : String)
  end
end

An assignment can be passed too, but in this case the type of the variable must be easily inferrable from the initial value:

class Person
  setter name = "John Doe"
end

Is the same as writing:

class Person
  @name = "John Doe"

  def name=(@name)
  end
end