ruby 哈希参数说明

Posted 2021-05-15

# Hash Method Arguments

def foo(b: 2, c: 3, **args)
  puts b #=> 2
  puts args #=> {a: 1, d: 4} 
end
# Usage: foo(a: 1, b: 2, c: 3, d: 4)


# Explination:

# Old way of hash arguments
def foo(args)
  puts args[:a]
  puts args[:b]
end

foo(a: 1, b: 2) 
#=> 1
#=> 2

# Default arguments and mixing ordinary arguments with hashes

def foo(a, args = {})
  defaults = {b: 2, c: 3}
  args = defaults.merge(args)
  puts a
  puts args
end

foo(1)
#=> 1 
#=> {b: 2, c: 3}

# Even better than default arguments, is keyword arguments (no merging default arguments).
# Mix them with Array arguments:

def foo(b: 2, c: 3, **args)
  puts b
  puts c
  puts args
end

foo(a: 1, b: 2, c: 3, d: 4)
#=> 2
#=> 3 
#=> {a: 1, d: 4} 

# Optional Args:

def foo(b: 2, c: 3, **args)
  puts b
  puts c
  puts args
end

foo(a: 1, b: 2, c: 3, d: 4)
#=> 2
#=> 3 
#=> {a: 1, d: 4}