对多个独立的if子句使用ruby on rails中的guard子句

Question

如何在以下场景中使用guard子句？msg在两个独立的if子句中捕获信息。

def edible?(food_object)
edible_type = ['fruit','vegetable','nuts']
food_list  = ['apple','banana','orange','olive','cashew','spinach']
food = food_object.food
type = food_object.type

msg = ''
if edible_type.include?(type)
msg += 'Edible : '
end
if food_list.include?(food)
msg += 'Great Choice !'
end
end

Answer 1

像这样：

def edible?(food_object)
edible_type = ['fruit','vegetable','nuts']
food_list  = ['apple','banana','orange','olive','cashew','spinach']
food = food_object.food
type = food_object.type

msg = ''
msg += 'Edible : ' if edible_type.include?(type)
msg += 'Great Choice !' if food_list.include?(food)
end

或尽早返回

def edible?(food_object)
edible_type = ['fruit','vegetable','nuts']
food_list  = ['apple','banana','orange','olive','cashew','spinach']
food = food_list.include?(food)
type = edible_type.include?(type)
msg = ''
return msg unless food || edible
msg += 'Edible : ' if type
msg += 'Great Choice !' if food
end

旁注：注意，通常接受的做法是，当ruby方法名称返回布尔值时，它们以?结尾。

Answer 2

我建议如下。

EDIBLE_TYPE = ['fruit','vegetable','nuts']
FOOD_LIST   = ['apple','banana','orange','olive','cashew','spinach']

def edible?(food_object)
"%s%s" % [EDIBLE_TYPE.include?(food_object.type) ? 'Edible : ' : '',
FOOD_LIST.include?(food_object.food)   ? 'Great Choice !' : '']
end

我们可以通过稍微修改方法来测试这一点。

def edible?(type, food)
"%s%s" % [EDIBLE_TYPE.include?(type) ? 'Edible : ' : '',
FOOD_LIST.include?(food)   ? 'Great Choice !' : '']
end

edible?('nuts', 'olive')     #=> "Edible : Great Choice !" 
edible?('nuts', 'kumquat')   #=> "Edible : " 
edible?('snacks', 'olive')   #=> "Great Choice !" 
edible?('snacks', 'kumquat') #=> "" 

该方法的操作线也可以写成：

format("%s%s", EDIBLE_TYPE.include?(food_object.type) ? 'Edible : ' : '',
FOOD_LIST.include?(food_object.food)   ? 'Great Choice !' : ''])

或

"#{EDIBLE_TYPE.include?(food_object.type) ? 'Edible : ' : ''}#{FOOD_LIST.include?(food_object.food) ? 'Great Choice !' : ''}"

请参阅内核#格式。