Question

在ruby抛出错误

中查找散列值数组的总和

parsed_response = [
  {"type"=>"trading", "currency"=>"btc", "amount"=>"1.19782496", "available"=>"1.19782496"},
  {"type"=>"trading", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"deposit", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"deposit", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"exchange", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"exchange", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}
]

parsed_response.map { |h| h["available"].to_f }.sum

这会引发以下错误：

undefined method `sum' for [1.19782496, 0.0, 0.0, 0.0, 0.0, 0.0]:Array (NoMethodError)

我应该如何更改我的代码？

Answer 1

因为，你只使用Ruby。你可以试试这个（因为Ruby中的数组没有sum方法）：

parsed_response.inject(0){|sum, response| sum = sum+response['available'].to_f }
#=> 1.19782496

如果您使用的是Rails，那么Enumerable中Array包含的sum方法可以像parsed_response.map { |h| h["available"].to_f }.sum #=> 1.19782496那样使用，可以这样使用：

{{1}}

Answer 2

Enumerable#sum是一种在vanilla Ruby中不存在的方法。相反，它是作为Ruby on Rails Web开发框架的一部分加载的扩展。

在vanilla Ruby中，一个合理的替代品是Enumerable#reduce：

parsed_response = [
  {"type"=>"trading", "currency"=>"btc", "amount"=>"1.19782496", "available"=>"1.19782496"},
  {"type"=>"trading", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"deposit", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"deposit", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"exchange", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"exchange", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}
]

parsed_response.map { |h| h["available"].to_f }.reduce(:+)
#=> 1.19782496

Answer 3

你的问题不清楚。

在积极支持下，应定义sum：

require 'active_support/all'
parsed_response = [{"type"=>"trading", "currency"=>"btc", "amount"=>"1.19782496", "available"=>"1.19782496"}, {"type"=>"trading", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"deposit", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"deposit", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"exchange", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"exchange", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}]
parsed_response.map { |h| h["available"].to_f }.sum
# => 1.19782496

如果没有有效支持，sum未定义，您应该使用inject(:+)代替：

parsed_response = [{"type"=>"trading", "currency"=>"btc", "amount"=>"1.19782496", "available"=>"1.19782496"}, {"type"=>"trading", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"deposit", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"deposit", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"exchange", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"}, {"type"=>"exchange", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}]
parsed_response.map { |h| h["available"].to_f }.inject(:+)
# => 1.19782496

如果您忘记to_f转换错误，您将连接所有字符串：

["1.19782496", "0.0", "0.0", "0.0", "0.0", "0.0"].inject(:+)
# => 1.197824960.00.00.00.00.0

Answer 4

实现这一目标的一种非常简单的方法：

result = 0.0
parsed_response.each do |item|
  result += item["available"].to_f
end

Answer 5

这有效：

parsed_response = [
  {"type"=>"trading", "currency"=>"btc", "amount"=>"1.19782496", "available"=>"1.19782496"},
  {"type"=>"trading", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"deposit", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"deposit", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"exchange", "currency"=>"btc", "amount"=>"0.0", "available"=>"0.0"},
  {"type"=>"exchange", "currency"=>"usd", "amount"=>"0.0", "available"=>"0.0"}
]

parsed_response.collect { |a| a["available"].to_f }.inject(:+)
#=> 1.19782496

在ruby中查找哈希值数组的总和

5 个答案: