[英]Ruby NoMethodError (undefined method ''…' for '…:Class'
require_relative 'json_lookup'
require_relative 'csv_lookup'
require_relative 'error'
BASE_RATE = 'EUR'
class CurrencyExchange
def initialize(file:, date:, from:, to:)
@file = file
@date = date
@from = from
@to = to
end
def rate
lookup = find_lookup
lookup.to_currency / lookup.from_currency
end
private
def find_lookup
case File.extname(@file)
when ".json"
JsonLookup.new(@file, @date, @from, @to)
when ".csv"
CsvLookup.new(@file, @date, @from, @to)
else raise FileError
end
end
end
当我在 irb 中运行 CurrencyExchange.rate 时,我不断收到此错误,所以我猜测 rate 方法出了点问题,但无法弄清楚原因。 但我可能遗漏了一些完全明显的东西......因为我是 Ruby 的完整初学者,将不胜感激任何帮助:)
回溯如下..
irb(main):003:0> CurrencyExchange.rate(Date.new(2018, 11, 22), "USD", "GBP") Traceback (most recent call last):
5: from C:/Ruby26-x64/bin/irb.cmd:31:in `<main>'
4: from C:/Ruby26-x64/bin/irb.cmd:31:in `load'
3: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
2: from (irb):3
1: from (irb):3:in `rescue in irb_binding'
NoMethodError (undefined method `rate' for CurrencyExchange:Class)
rate
是您示例中的实例方法,但CurrencyExchange.rate
尝试调用 class 方法。
为了解决这个问题,首先初始化一个实例并调用然后对该实例进行rate
。 此外, rate
不接受 arguments,您需要将变量传递给初始化方法。
currency_exchange = CurrencyExchange.new(
file: file, date: Date.new(2018, 11, 22), from: "USD", to: "GBP"
)
currency_exchange.rate
注意初始化器需要 4 个名为 arguments。 您还需要将文件传递给new
方法。
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