abstract struct Enum
Overview
Enum is the base type of all enums.
An enum is a set of integer values, where each value has an associated name. For example:
enum Color Red # 0 Green # 1 Blue # 2 end
Values start with the value 0
and are incremented by one, but can be overwritten.
To get the underlying value you invoke value on it:
Color::Green.value # => 1
Each constant (member) in the enum has the type of the enum:
typeof(Color::Red) # => Color
Flags enum
An enum can be marked with the @[Flags]
annotation. This changes the default values:
@[Flags] enum IOMode Read # 1 Write # 2 Async # 4 end
Additionally, some methods change their behaviour.
Enums from integers
An enum can be created from an integer:
Color.new(1).to_s # => "Green"
Values that don't correspond to enum's constants are allowed: the value will still be of type Color, but when printed you will get the underlying value:
Color.new(10).to_s # => "10"
This method is mainly intended to convert integers from C to enums in Crystal.
Question methods
An enum automatically defines question methods for each member, using String#underscore
for the method name.
- In the case of regular enums, this compares by equality (
#==
). - In the case of flags enums, this invokes
#includes?
.
For example:
color = Color::Blue color.red? # => false color.blue? # => true mode = IOMode::Read | IOMode::Async mode.read? # => true mode.write? # => false mode.async? # => true
This is very convenient in case
expressions:
case color when .red? puts "Got red" when .blue? puts "Got blue" end
Included Modules
Defined in:
enum.crjson/to_json.cr
yaml/to_yaml.cr
Constructors
- .from_value(value : Int) : self
Returns the enum member that has the given value, or raises if no such member exists.
- .from_value?(value : Int) : self?
Returns the enum member that has the given value, or
nil
if no such member exists. - .new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
Reads a serialized enum member by name from ctx and node.
- .new(value : self)
Returns value.
- .new(pull : JSON::PullParser)
Reads a serialized enum member by name from pull.
- .parse(string : String) : self
Returns the enum member that has the given name, or raises
ArgumentError
if no such member exists. - .parse?(string : String) : self?
Returns the enum member that has the given name, or
nil
if no such member exists.
Class Method Summary
- .each(& : self -> )
Iterates each member of the enum.
- .names : Array(String)
- .valid?(value : self) : Bool
Returns
true
if the given value is an enum member, otherwisefalse
. - .values : Array(self)
Returns all enum members as an
Array(self)
.
Instance Method Summary
- #&(other : self) : self
Returns the enum member that results from applying a logical "and" operation between this enum member's value and other.
- #+(other : Int) : self
Returns the enum member that results from adding other to this enum member's value.
- #-(other : Int) : self
Returns the enum member that results from subtracting other to this enum member's value.
- #<=>(other : self)
Compares this enum member against another, according to their underlying value.
- #==(other : self)
Returns
true
if this enum member and other have the same underlying value. - #==(other)
Returns
false
. - #^(other : self) : self
Returns the enum member that results from applying a logical "xor" operation between this enum member's value and other.
- #clone
- #each(& : self -> )
Iterates each values in a Flags Enum.
- #hash(hasher)
- #includes?(other : self) : Bool
Returns
true
if this enum member's value includes other. - #to_f32 : Float32
Returns the value of this enum member as a
Float32
- #to_f32! : Float32
Returns the value of this enum member as a
Float32
- #to_f64 : Float64
Returns the value of this enum member as a
Float64
- #to_f64! : Float64
Returns the value of this enum member as a
Float64
- #to_i : Int32
Returns the value of this enum member as an
Int32
. - #to_i16 : Int16
Returns the value of this enum member as a
Int16
- #to_i16! : Int16
Returns the value of this enum member as a
Int16
- #to_i32 : Int32
Returns the value of this enum member as a
Int32
- #to_i32! : Int32
Returns the value of this enum member as a
Int32
- #to_i64 : Int64
Returns the value of this enum member as a
Int64
- #to_i64! : Int64
Returns the value of this enum member as a
Int64
- #to_i8 : Int8
Returns the value of this enum member as a
Int8
- #to_i8! : Int8
Returns the value of this enum member as a
Int8
- #to_json(json : JSON::Builder)
Serializes this enum member by name.
- #to_s(io : IO) : Nil
Appends a
String
representation of this enum member to the given io. - #to_s : String
Returns a
String
representation of this enum member. - #to_u16 : UInt16
Returns the value of this enum member as a
UInt16
- #to_u16! : UInt16
Returns the value of this enum member as a
UInt16
- #to_u32 : UInt32
Returns the value of this enum member as a
UInt32
- #to_u32! : UInt32
Returns the value of this enum member as a
UInt32
- #to_u64 : UInt64
Returns the value of this enum member as a
UInt64
- #to_u64! : UInt64
Returns the value of this enum member as a
UInt64
- #to_u8 : UInt8
Returns the value of this enum member as a
UInt8
- #to_u8! : UInt8
Returns the value of this enum member as a
UInt8
- #to_yaml(yaml : YAML::Nodes::Builder)
Serializes this enum member by name.
- #|(other : self) : self
Returns the enum member that results from applying a logical "or" operation between this enum member's value and other.
- #~ : self
Returns the enum member that results from applying a logical "not" operation of this enum member's value.
Macro Summary
- flags(*values)
Convenience macro to create a combined enum (combines given members using
#|
(or) logical operator)
Instance methods inherited from module Comparable(Enum)
<, <=(other : T) <=, <=>(other : T) <=>, ==(other : T) ==, >(other : T) : Bool >, >=(other : T) >=, clamp(min, max)clamp(range : Range) clamp
Instance methods inherited from struct Value
==(other : JSON::Any)==(other : YAML::Any)
==(other) ==, dup dup
Instance methods inherited from class Object
! : Bool !, !=(other) !=, !~(other) !~, ==(other) ==, ===(other : JSON::Any)===(other : YAML::Any)
===(other) ===, =~(other) =~, as(type : Class) as, as?(type : Class) as?, class class, dup dup, hash(hasher)
hash hash, in?(collection : Object) : Bool
in?(*values : Object) : Bool in?, inspect(io : IO) : Nil
inspect : String inspect, is_a?(type : Class) : Bool is_a?, itself itself, nil? : Bool nil?, not_nil! not_nil!, pretty_inspect(width = 79, newline = "\n", indent = 0) : String pretty_inspect, pretty_print(pp : PrettyPrint) : Nil pretty_print, responds_to?(name : Symbol) : Bool responds_to?, tap(&) tap, to_json(io : IO) : Nil
to_json : String to_json, to_pretty_json(indent : String = " ") : String
to_pretty_json(io : IO, indent : String = " ") : Nil to_pretty_json, to_s(io : IO) : Nil
to_s : String to_s, to_yaml(io : IO) : Nil
to_yaml : String to_yaml, try(&) try, unsafe_as(type : T.class) forall T unsafe_as
Class methods inherited from class Object
from_json(string_or_io, root : String)from_json(string_or_io) from_json, from_yaml(string_or_io : String | IO) from_yaml
Constructor Detail
def self.from_value(value : Int) : selfSource
Returns the enum member that has the given value, or raises if no such member exists.
Color.from_value(0) # => Color::Red Color.from_value(1) # => Color::Green Color.from_value(2) # => Color::Blue Color.from_value(3) # raises Exception
def self.from_value?(value : Int) : self?Source
Returns the enum member that has the given value, or nil
if no such member exists.
Color.from_value?(0) # => Color::Red Color.from_value?(1) # => Color::Green Color.from_value?(2) # => Color::Blue Color.from_value?(3) # => nil
def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)Source
Reads a serialized enum member by name from ctx and node.
See #to_yaml
for reference.
Raises YAML::ParseException
if the deserialization fails.
def self.new(value : self)Source
Returns value.
def self.new(pull : JSON::PullParser)Source
Reads a serialized enum member by name from pull.
See #to_json
for reference.
Raises JSON::ParseException
if the deserialization fails.
def self.parse(string : String) : selfSource
Returns the enum member that has the given name, or raises ArgumentError
if no such member exists. The comparison is made by using String#camelcase
and String#downcase
between string and the enum members names, so a member named "FortyTwo" or "FORTY_TWO" is found with any of these strings: "forty_two", "FortyTwo", "FORTY_TWO", "FORTYTWO", "fortytwo".
Color.parse("Red") # => Color::Red Color.parse("BLUE") # => Color::Blue Color.parse("Yellow") # raises ArgumentError
def self.parse?(string : String) : self?Source
Returns the enum member that has the given name, or nil
if no such member exists. The comparison is made by using String#camelcase
and String#downcase
between string and the enum members names, so a member named "FortyTwo" or "FORTY_TWO" is found with any of these strings: "forty_two", "FortyTwo", "FORTY_TWO", "FORTYTWO", "fortytwo".
Color.parse?("Red") # => Color::Red Color.parse?("BLUE") # => Color::Blue Color.parse?("Yellow") # => nil
Class Method Detail
def self.each(& : self -> )Source
Iterates each member of the enum. It won't iterate the None
and All
members of flags enums.
IOMode.each do |member, value| # yield IOMode::Read, 1 # yield IOMode::Write, 2 # yield IOMode::Async, 3 end
def self.valid?(value : self) : BoolSource
Returns true
if the given value is an enum member, otherwise false
. false
if not member.
Color.valid?(Color::Red) # => true Color.valid?(Color.new(4)) # => false
NOTE This is a class method, not an instance method because an instance method .valid?
is defined by the language when a user defines an enum member named Valid
.
def self.values : Array(self)Source
Returns all enum members as an Array(self)
.
Color.values # => [Color::Red, Color::Green, Color::Blue]
Instance Method Detail
def &(other : self) : selfSource
Returns the enum member that results from applying a logical "and" operation between this enum member's value and other. This is mostly useful with flag enums.
(IOMode::Read | IOMode::Async) & IOMode::Read # => IOMode::Read
def +(other : Int) : selfSource
Returns the enum member that results from adding other to this enum member's value.
Color::Red + 1 # => Color::Green Color::Red + 2 # => Color::Blue Color::Red + 3 # => Color.new(3)
def -(other : Int) : selfSource
Returns the enum member that results from subtracting other to this enum member's value.
Color::Blue - 1 # => Color::Green Color::Blue - 2 # => Color::Red Color::Blue - 3 # => Color.new(-1)
def <=>(other : self)Source
Compares this enum member against another, according to their underlying value.
Color::Red <=> Color::Blue # => -1 Color::Blue <=> Color::Red # => 1 Color::Blue <=> Color::Blue # => 0
def ==(other : self)Source
Returns true
if this enum member and other have the same underlying value.
Color::Red == Color::Red # => true Color::Red == Color::Blue # => false
def ^(other : self) : selfSource
Returns the enum member that results from applying a logical "xor" operation between this enum member's value and other. This is mostly useful with flag enums.
def cloneSource
def each(& : self -> )Source
Iterates each values in a Flags Enum.
(IOMode::Read | IOMode::Async).each do |member, value| # yield IOMode::Read, 1 # yield IOMode::Async, 3 end
def hash(hasher)Source
def includes?(other : self) : BoolSource
Returns true
if this enum member's value includes other. This performs a logical "and" between this enum member's value and other's, so instead of writing:
(member & value) != 0
you can write:
member.includes?(value)
The above is mostly useful with flag enums.
For example:
mode = IOMode::Read | IOMode::Write mode.includes?(IOMode::Read) # => true mode.includes?(IOMode::Async) # => false
def to_i : Int32Source
Returns the value of this enum member as an Int32
.
Color::Blue.to_i # => 2 (IOMode::Read | IOMode::Write).to_i # => 3 Color.new(10).to_i # => 10
def to_json(json : JSON::Builder)Source
Serializes this enum member by name.
For non-flags enums, the serialization is a JSON string. The value is the member name (see #to_s
) transformed with String#underscore
.
enum Stages INITIAL SECOND_STAGE end Stages::INITIAL.to_json # => %("initial") Stages::SECOND_STAGE.to_json # => %("second_stage")
For flags enums, the serialization is a JSON array including every flagged member individually serialized in the same way as a member of a non-flags enum. None
is serialized as an empty array, All
as an array containing all members.
@[Flags] enum Sides LEFT RIGHT end Sides::LEFT.to_json # => %(["left"]) (Sides::LEFT | Sides::RIGHT).to_json # => %(["left","right"]) Sides::All.to_json # => %(["left","right"]) Sides::None.to_json # => %([])
ValueConverter.to_json
offers a different serialization strategy based on the member value.
def to_s : StringSource
Returns a String
representation of this enum member. In the case of regular enums, this is just the name of the member. In the case of flag enums, it's the names joined by vertical bars, or "None", if the value is zero.
If an enum's value doesn't match a member's value, the raw value is returned as a string.
Color::Red.to_s # => "Red" IOMode::None.to_s # => "None" (IOMode::Read | IOMode::Write).to_s # => "Read | Write" Color.new(10).to_s # => "10"
def to_yaml(yaml : YAML::Nodes::Builder)Source
Serializes this enum member by name.
For non-flags enums, the serialization is a YAML string. The value is the member name (see #to_s
) transformed with String#underscore
.
enum Stages INITIAL SECOND_STAGE end Stages::INITIAL.to_yaml # => %(--- initial\n) Stages::SECOND_STAGE.to_yaml # => %(--- second_stage\n)
For flags enums, the serialization is a YAML sequence including every flagged member individually serialized in the same way as a member of a non-flags enum. None
is serialized as an empty sequence, All
as a sequence containing all members.
@[Flags] enum Sides LEFT RIGHT end Sides::LEFT.to_yaml # => %(--- [left]\n) (Sides::LEFT | Sides::RIGHT).to_yaml # => %(--- [left, right]\n) Sides::All.to_yaml # => %(--- [left, right]\n) Sides::None.to_yaml # => %(--- []\n)
ValueConverter.to_yaml
offers a different serialization strategy based on the member value.
def |(other : self) : selfSource
Returns the enum member that results from applying a logical "or" operation between this enum member's value and other. This is mostly useful with flag enums.
(IOMode::Read | IOMode::Async) # => IOMode::Read | IOMode::Async
def ~ : selfSource
Returns the enum member that results from applying a logical "not" operation of this enum member's value.
Macro Detail
macro flags(*values)Source
Convenience macro to create a combined enum (combines given members using #|
(or) logical operator)
IOMode.flags(Read, Write) # => IOMode::Read | IOMode::Write
© 2012–2021 Manas Technology Solutions.
Licensed under the Apache License, Version 2.0.
https://crystal-lang.org/api/1.2.1/Enum.html