Pytanie 1¶
Do czego najbardziej mogą przydać się nam zagnieżdżone klasy i interfejsy?
Pytanie 2¶
Czy Java Developer powinien się zaznajamiać głęboko z wyrażeniami lambda wprowadzonymi w Java 8 pomimo spadków wydajności przy używaniu paralelizmu, utrudnionego debugowania ze względu na wydłużone "stack trace"?
Pytanie 3¶
Jeśli w klasie wewnętrznej zostanie zadeklarowana zmienna tego samego typu i o tej samej nazwie co w klasie otaczającej to czy przesłoni ona tę z otaczającej?
Pomoc wbudowana w REPLa¶
In [ ]:
[1] pry(main)> require 'dry/types'
=> true
[2] pry(main)> ls Dry
constants: Configurable Container Core Equalizer Logic Types
Dry.methods: Equalizer
[3] pry(main)> ls Dry::Equalizer
constants: Methods
Object.methods: yaml_tag
Module.methods: constants nesting used_modules
[4] pry(main)> ? Dry::Equalizer#constants
From: variable.c (C Method):
Owner: Module
Visibility: public
Signature: constants(*arg1)
Number of lines: 12
Returns an array of the names of the constants accessible in
mod. This includes the names of constants in any included
modules (example at start of section), unless the inherit
parameter is set to false.
The implementation makes no guarantees about the order in which the
constants are yielded.
IO.constants.include?(:SYNC) #=> true
IO.constants(false).include?(:SYNC) #=> false
Also see Module::const_defined?.
Informacja o typie¶
In [29]:
puts 1.class()
puts "Ala ma kota".class()
Weryfikacja przynależności do typu¶
In [30]:
object = "Ala ma kota"
if(object.is_a?(String))
puts "Obiekt jest łańcuchem znaków"
end
In [31]:
object = "Ala ma kota"
if(String === object)
puts "Obiekt jest łańcuchem znaków"
end
In [32]:
object = [1,2,3]
case(object)
when String
puts "Obiekt jest łańuchem znaków"
when Array
puts "Obiekt jest tablicą"
end
Informacje o hierarchii klas¶
In [41]:
class Animal
end
class Mammal < Animal
end
class Cat < Mammal
end
class Bat < Mammal
end
puts Cat.new
puts Cat.new.class
puts Cat.new.class.superclass
puts Cat.new.class.class
puts Cat.new.class.class.class.superclass.superclass.superclass.superclass
In [42]:
def ancestors(klass, chain=[])
klass.superclass ? ancestors(klass.superclass, chain + [klass]) : chain.reverse
end
puts ancestors(Bat)
In [43]:
class Whale < Mammal
end
class Reptile < Animal
end
class Snake < Reptile
end
In [44]:
[1,2,3].zip(["a", "b", "c"]).to_a
Out[44]:
In [45]:
[1,2,3,4,5,6].each_cons(2).to_a
Out[45]:
In [46]:
[1,2,3,4,5].
zip(["a", "b", "c", "d", "e"]).
each_cons(2).
each{|(a1, b1), (a2,b2)| puts "#{a1} - #{b1} : #{a2} - #{b2}"}
In [47]:
def commonAncestor(klass1, klass2)
ancestors(klass1).zip(ancestors(klass2)).each_cons(2) do |(grandparent1, grandparent2), (parent1, parent2)|
return grandparent1 if parent1 != parent2
end
end
Out[47]:
In [48]:
puts commonAncestor(Bat, Whale)
puts commonAncestor(Snake, Bat)
puts commonAncestor(Snake, Reptile)
puts commonAncestor(1.class, Bat)
Dynamiczne ładowanie klas¶
In [49]:
class Car
def go
puts "Brum brum"
end
end
class Airplane
def go
puts "Bzzzzz"
end
end
class Rocket
def go
puts "BUUUUUUM"
end
end
Out[49]:
In [50]:
["Car", "Car", "Rocket", "Airplane"].each do |classname|
Class.const_get(classname).new.go
end
Out[50]:
Refleksja¶
In [51]:
puts Car.new.public_methods.sort
In [52]:
puts (Car.new.public_methods - 1.public_methods).sort
In [53]:
class Bike
def initialize
@speed = 0
end
def go
@speed = 10
end
def stop
@speed = 0
end
def riding?
@speed > 0
end
end
Out[53]:
In [54]:
puts Bike.new.instance_variables
Dynamiczne wywoływanie metod¶
In [55]:
bike = Bike.new
puts bike.public_send("riding?")
bike.public_send("go")
puts bike.public_send("riding?")
In [57]:
bike = Bike.new
#bike.public_send("initialize")
bike.send("initialize")
Out[57]:
Dynamiczny dostęp do pól¶
In [62]:
bike = Bike.new
puts bike.instance_variable_get("@speed")
bike.instance_variable_set("@speed", 10)
puts bike.instance_variable_get("@speed")
In [61]:
class Bike
def instance_variable_set(name, value)
raise "Don't do it!"
end
end
Out[61]:
In [ ]:
bike = Bike.new
puts bike.instance_variable_get("@speed")
bike.instance_variable_set("@speed", 10)
puts bike.instance_variable_get("@speed")
Dynamiczne proxy¶
In [63]:
class Wrapper
def initialize(object)
@object = object
@invocations = []
end
def method_missing(*arguments)
@invocations << arguments
@object.public_send(*arguments)
end
def replay
@invocations.each do |arguments|
@object.public_send(*arguments)
end
end
end
Out[63]:
In [64]:
wrapper = Wrapper.new([])
wrapper << 1
wrapper << 2
wrapper << 3
puts wrapper.to_a.join(", ")
wrapper.replay
puts wrapper.to_a.join(", ")