ruby1.8到2.1语法改变

1定义hash的语法改变
old_way = {:foo => "bar", :one => 1}
new_way = {foo: "bar", one: 1}

2 方法中传递hash

def some_method(hash = {})
# do stuff
end
some_method(:foo => "bar")
some_method(foo: "bar")

3 hash中key做参数

# OLD
def old_way(options={})
return options[:foo]
end

old_way(:foo => "bar") # => "bar"
old_way #=>nil

# NEW UNNAMED KEYWORD ARGUMENTS
def new_way(**options)
return options[:foo]
end
# => :new_way

new_way(foo: "bar" ) # => "bar"
new_way b# => nil

hash中的key可以作为默认的方法参数
# NEW NAMED KEYWORD ARGUMENTS
def new_way(foo:)
return foo
end
# => :new_way

new_way(foo: "bar") # => "bar"
new_way # ArgumentError: missing keyword: foo

定义proc的新语法

old_way = Proc.new { |a, b| a + b }
old_way.call(1, 2)
# => 3

new_way = ->(a, b) { a + b }
new_way.call(1, 2)
# => 3

生成符号数组

old_way = [:foo, :bar, :baz]
new_way = %i(foo bar baz)

定义有理数方法
old_way = Rational(6, 5)
new_way = 1.2r

关键字参数

def foo(a, b="b_default", *c, d:, e: "e_default", **f, &g)
# do stuff
end
a: 必须有的参数
b:可选的参数有一个默认值
c: 通常接受多个参数存为数组
d: 关键字参数
e:关键字参数有默认值
f:接收参数存为hash
g:块参数