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Feature #15192

Updated by jjyr (Jinyang Jiang) about 1 year ago

Motivation:

Introduce a new syntax for convenient setup instance variables for objects.

The problem:

Currently, setup instance variables in Ruby is too verbose.
Basically, we need to write the meaningless assigning code again and again to assign variables

``` ruby
class Person
def initialize(name:, age:, gender:, country:)
@name = name
@age = age
@gender = gender
@country = country
end
end

# we can use Struct to avoiding this

Person = Struct.new(:name, :age, :gender, :country, keyword_init: true)

# let's see a real-world case, which can't use Struct to describe an initializing process, from https://github.com/ciri-ethereum/ciri/blob/748985ccf7a620a2e480706a5a6b38f56409d487/lib/ciri/devp2p/server.rb#L54
# Because we want to do something more than just assigning instance variables

class Server
def initialize(private_key:, protocol_manage:, bootstrap_nodes: [],
node_name: 'Ciri', tcp_host: '127.0.0.1', tcp_port: 33033)
@private_key = private_key
@node_name = node_name
@bootstrap_nodes = bootstrap_nodes
@protocol_manage = protocol_manage
server_node_id = NodeID.new(@private_key)
caps = [Cap.new(name: 'eth', version: 63)]
@handshake = ProtocolHandshake.new(version: BASE_PROTOCOL_VERSION, name: @node_name, id: server_node_id.id, caps: caps)
@tcp_host = tcp_host
@tcp_port = tcp_port
@dial = Dial.new(bootstrap_nodes: bootstrap_nodes, private_key: private_key, handshake: @handshake)
@network_state = NetworkState.new(protocol_manage)
@dial_scheduler = DialScheduler.new(@network_state, @dial)
end
end

# Introduce a new "shortcut assigning" syntax for convenient setup

class Person
# use @ prefix to describe instance variables.
def initialize(@name:, @age:, @gender:, @country:)
end

# equal to
def initialize2(name:, age:, gender:, country:)
@name = name
@age = age
@gender = gender
@country = country
end

# it should also work on position style arguments
def initialize2(@name, @age, @gender, @country)
end
end

# Our real-world case can be rewritten as below
class Server
def initialize(@private_key:, @protocol_manage:, @bootstrap_nodes: [],
@node_name: 'Ciri', @tcp_host: '127.0.0.1', @tcp_port: 33033)
server_node_id = NodeID.new(@private_key)
caps = [Cap.new(name: 'eth', version: 63)]
@handshake = ProtocolHandshake.new(version: BASE_PROTOCOL_VERSION, name: @node_name, id: server_node_id.id, caps: caps)
@dial = Dial.new(bootstrap_nodes: @bootstrap_nodes, private_key: @private_key, handshake: @handshake)
@network_state = NetworkState.new(@protocol_manage)
@dial_scheduler = DialScheduler.new(@network_state, @dial)
end
end

# consider to keep consistency, insistence, this "shortcut assigning" syntax should work for non-initialize methods
class Foo
def bar(@still_works)
p @still_works
end
end
```

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