value
initialize
方法中的变量LocationList
填充在第014行。这些更改由第015行中的print
语句重新选择,但是{{{行016中的1}}认为哈希值仍为空(向右滚动以查看return
之后的返回值)。
=>
在全局函数中执行基本相同的操作会产生预期的返回值:
def random_point
x = rand * 2.0 - 1.0
y = rand * 2.0 - 1.0
until x**2 + y**2 < 1.0
x = rand * 2.0 - 1.0
y = rand * 2.0 - 1.0
end
return [x, y]
end
class LocationList < Hash
def initialize(node_list)
value = {}
node_list.each {|node| value[node] = random_point }
print value
return value
end
end
z = ["moo", "goo", "gai", "pan"]
LocationList.new(z)
#=> {"moo"=>[0.17733298257484997, 0.39221824315332987], "goo"=>[-0.907202436634851, 0.3589265999520428], "gai"=>[0.3910479677151635, 0.5624531973759821], "pan"=>[-0.37544369339427974, -0.7603500269538608]}=> {}
答案 0 :(得分:5)
您正在创建一个新的哈希,在value
方法中调用initialize
,而不是初始化self
。说明这内联:
class LocationList < Hash
def initialize(node_list)
# self is already a LocationList, which is a Hash
value={}
# value is now a new Hash
node_list.each {|node| value[node]=random_point}
# value now has keys set
return value
# value is now discarded
# LocationList.new returns the constructed object; it does not return
# the result of LocationList#initialize
end
end
请改为尝试:
class LocationList < Hash
def initialize(node_list)
node_list.each {|node| self[node]=random_point}
end
end
答案 1 :(得分:2)
请注意,您实际上并未拨打initialize
,而是拨打new
,然后拨打initialize
。 new
抛弃了initialize
的返回值,而是始终返回刚刚创建的对象。在the implementation of Class#new
中可以清楚地看到这一点。
由于你已经在你想要的哈希中,不要创建另一个哈希(value
),只需使用你所在的哈希(self
)!这会将initialize
缩减为:
def initialize(node_list)
node_list.each { |node| self[node] = random_point }
end