[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
當我在 irb 中運行 CurrencyExchange.rate 時,我不斷收到此錯誤,所以我猜測 rate 方法出了點問題,但無法弄清楚原因。 但我可能遺漏了一些完全明顯的東西......因為我是 Ruby 的完整初學者,將不勝感激任何幫助:)
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
是您示例中的實例方法,但CurrencyExchange.rate
嘗試調用 class 方法。
為了解決這個問題,首先初始化一個實例並調用然后對該實例進行rate
。 此外, rate
不接受 arguments,您需要將變量傳遞給初始化方法。
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 個名為 arguments。 您還需要將文件傳遞給new
方法。
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