Ruby 通过阵列时消除重复

我有不同的包含单位的散列，分组为单位类型。我的代码旨在确定应该返回哪个单元类型以进行进一步处理。然而，在检查每一份清单时，都会有大量重复。第一个if的操作与第一个elsif完全相同。如何以最好的方式使代码变干

from_unit = "gr"
to_unit = "kg"

WEIGHT = {
"gr" => 1000.0,
"kg" => 1.0,
}

MEASURE = {
"mm" => 1000.0,
"cm" => 100.0,
"m" => 1.0
}

if WEIGHT.has_key?(from_unit) or WEIGHT.has_key?(to_unit)
  if WEIGHT.has_key?(from_unit) && WEIGHT.has_key?(to_unit)
    return WEIGHT
  elsif WEIGHT.has_key?(from_unit)
    raise RuntimeError, "#{to_unit} is not a known unit"
  else
    raise RuntimeError, "#{from_unit} is not a known unit"
  end
elsif MEASURE.has_key?(from_unit) or MEASURE.has_key?(to_unit)
  if MEASURE.has_key?(from_unit) && MEASURE.has_key?(to_unit)
    return WEIGHT
  elsif MEASURE.has_key?(from_unit)
    raise RuntimeError, "#{to_unit} is not a known unit"
  else
    raise RuntimeError, "#{from_unit} is not a known unit"
  end
else
  raise RuntimeError, "You can't convert #{from_unit} into #{to_unit}"
end

---

你可以这样做：

if !MEASURE.has_key?(from_unit) and !WEIGHT.has_key?(from_unit)
    raise RuntimeError, "#{from_unit} is not a known unit"

if !MEASURE.has_key?(to_unit) and !WEIGHT.has_key?(to_unit)
    raise RuntimeError, "#{to_unit} is not a known unit"

if WEIGHT.has_key?(from_unit) and WEIGHT.has_key?(to_unit)
    return WEIGHT

if MEASURE.has_key?(from_unit) and MEASURE.has_key?(to_unit)
    return MEASURE # Was this a typo?

raise RuntimeError, "You can't convert #{from_unit} into #{to_unit}"

---

你可以这样做：

if !MEASURE.has_key?(from_unit) and !WEIGHT.has_key?(from_unit)
    raise RuntimeError, "#{from_unit} is not a known unit"

if !MEASURE.has_key?(to_unit) and !WEIGHT.has_key?(to_unit)
    raise RuntimeError, "#{to_unit} is not a known unit"

if WEIGHT.has_key?(from_unit) and WEIGHT.has_key?(to_unit)
    return WEIGHT

if MEASURE.has_key?(from_unit) and MEASURE.has_key?(to_unit)
    return MEASURE # Was this a typo?

raise RuntimeError, "You can't convert #{from_unit} into #{to_unit}"

---

为了简单起见，此代码段比您的代码段进行的检查要少（真的有必要吗？），但可以完成以下工作：

def get_table(from_unit, to_unit)
  [WEIGHT, MEASURE].detect do |table|
    table[from_unit] && table[to_unit]
  end or fail("You can't convert #{from_unit} into #{to_unit}")
end

---

为了简单起见，此代码段比您的代码段进行的检查要少（真的有必要吗？），但可以完成以下工作：

def get_table(from_unit, to_unit)
  [WEIGHT, MEASURE].detect do |table|
    table[from_unit] && table[to_unit]
  end or fail("You can't convert #{from_unit} into #{to_unit}")
end

---

Cf.您可以使用

|

&&

或

和
或
（布尔表达式的惯用用法是第一个），但不要将它们混合使用！另外，不要编写一个显式的
返回
，它也不是惯用的。Cf。您可以使用
|
&&
或
和
或
（布尔表达式的惯用用法是第一个），但不要混用它们！另外，不要编写一个显式的
返回
，它也不是惯用的。