红宝石浮动算术阵列

Question

我在数组成员（浮动）上做数学。类型看起来正确。我仍然得到奇怪的错误。根本没有nil价值。这个错误是什么？

nil can't be coerced into Float 

步骤1

newFront = [412.5, 312.5] 
@direction = [1.0, 0.0] 
@length = 50.0 
retRear = [newFront[0] - (@direction[0] * @lenght), newFront[1] - (@direction[1] * @lenght)] 
# => TypeError: nil can't be coerced into Float 
# from (irb):13:in `*' 
# from (irb):13 
# from /usr/bin/irb:12:in `<main>' 

步骤2

newFront[0].class # => Float 
@direction[0].class # => Float 
@length.class # => Float 

步骤3

nfx = Float(newFront[0]) # => 412.5 
dx = Float(@direction[0]) # => 1.0 
nfy = Float(newFront[1]) # => 312.5 
dy = Float(@direction[1]) # => 0.0 
@l = 50.0 
retRear = [nfx - (dx * @l), nfy - (dy * @l)] # => [362.5, 312.5] 

这就是我想要的。 Ruby是否想告诉我，我根本不能使用Arrays进行Float算术？此外，重写相同的表达式也会失败。

retRear = [Float(newFront[0]) - (Float(@direction[0]) * Float(@lenght)), Float(newFront[1]) - (Float(@direction[1]) * Float(@lenght))] 
# => TypeError: can't convert nil into Float 
# from (irb):78:in `Float' 
# from (irb):78 
# from /usr/bin/irb:12:in `<main>' 

Answer 1

As @WallyAltman指出，你拼写错误@length，因此为零。

我会做这种方式，顺便说一句：

new_front = [412.5, 312.5] 
@direction = [1.0, 0.0] 
@length = 50.0 
ret_rear = new_front.zip(@direction).map do |front, dir| 
    front - dir * @length 
end 
# => [362.5, 312.5] 

Answer 2

的零是从您的错字到来。 @length设置为50，但没有为变量@lenght设置值（注意转置的“h”和“t”）。

Answer 3

你有一个错字 - @lenght而不是@length。