我从SQL查询得到items的结果。我想使用这些结果来创建一个名为products的新哈希数组。我所走的道路似乎并不合适。迭代每一行时，我需要对行中的一些键进行条件处理，例如下面的伪代码。
items = retrieve_items_from_db
products = items.map do |row|
{
row.each do | k, v|
if k == "Color"
#go do something and add updated key, value pair to products
else puts "SKEY:#{k} VALUE: #{v}"
# add k,v to products
k => v
end
}
end
任何指针或建议？我尝试使用inject({})代替map。
答案 0 :(得分：0)
你在这里尝试做的事情很酷，但我们不能把条件陈述放在哈希中。
即。你做不到：
{
if 2 == 2
math: "correct"
else
math: "incorrect"
end
}
你需要改为：
if 2 == 2
{ math: "correct" }
else
{ math: "incorrect" }
end
如果您需要将多个哈希合并为一个，Hash#merge方法很有用。
例如：
{ a: "a", b: "DEFAULT" }.merge({ b: "b", c: "c" })
# => { a: "a", b: "b", c: "c" }
您可以看到第二个哈希在第一个哈希中覆盖了值。
您可以在这里使用inject（或reduce，它可以做同样的事情，但听起来不那么可怕），但是因为您要将数组转换为数组，所以＆＃39 ; d更容易使用map。
products = items.map do |row|
if row.keys.include?(:price)
row = row.merge(price: "#{row[:price]} dollars")
else
row = row.merge(price: "not available for sale")
end
next row
end
答案 1 :(得分：0)
使其成为嵌套映射，然后展平：
Tue Apr 05 15:09:34 2016
('1% | |',)
('2% |> |',)
('3% |> |',)
('4% |=> |',)
('5% |=> |',)
('6% |==> |',)
('7% |==> |',)
('8% |===> |',)
('9% |===> |',)
('10% |====> |',)
('11% |====> |',)
('12% |=====> |',)
('13% |=====> |',)
('14% |======> |',)
('15% |======> |',)
('16% |=======> |',)
('17% |=======> |',)
('18% |========> |',)
('19% |========> |',)
('20% |=========> |',)
('21% |=========> |',)
('22% |==========> |',)
('23% |==========> |',)
('24% |===========> |',)
('25% |===========> |',)
('26% |============> |',)
('27% |============> |',)
('28% |=============> |',)
('29% |=============> |',)
('30% |==============> |',)
('31% |==============> |',)
('32% |===============> |',)
('33% |===============> |',)
('34% |================> |',)
('35% |================> |',)
('36% |=================> |',)
('37% |=================> |',)
('38% |==================> |',)
('39% |==================> |',)
('40% |===================> |',)
('41% |===================> |',)
('42% |====================> |',)
('43% |====================> |',)
('44% |=====================> |',)
('45% |=====================> |',)
('46% |======================> |',)
('47% |======================> |',)
('48% |=======================> |',)
('49% |=======================> |',)
('50% |========================> |',)
('51% |========================> |',)
('52% |=========================> |',)
('53% |=========================> |',)
('54% |==========================> |',)
('55% |==========================> |',)
('56% |===========================> |',)
('57% |===========================> |',)
('58% |============================> |',)
('59% |============================> |',)
('60% |=============================> |',)
('61% |=============================> |',)
('62% |==============================> |',)
('63% |==============================> |',)
('64% |===============================> |',)
('65% |===============================> |',)
('66% |================================> |',)
('67% |================================> |',)
('68% |=================================> |',)
('69% |=================================> |',)
('70% |==================================> |',)
('71% |==================================> |',)
('72% |===================================> |',)
('73% |===================================> |',)
('74% |====================================> |',)
('75% |====================================> |',)
('76% |=====================================> |',)
('77% |=====================================> |',)
('78% |======================================> |',)
('79% |======================================> |',)
('80% |=======================================> |',)
('81% |=======================================> |',)
('82% |========================================> |',)
('83% |========================================> |',)
('84% |=========================================> |',)
('85% |=========================================> |',)
('86% |==========================================> |',)
('87% |==========================================> |',)
('88% |===========================================> |',)
('89% |===========================================> |',)
('90% |============================================> |',)
('91% |============================================> |',)
('92% |=============================================> |',)
('93% |=============================================> |',)
('94% |==============================================> |',)
('95% |==============================================> |',)
('96% |===============================================> |',)
('97% |===============================================> |',)
('98% |================================================> |',)
Tue Apr 05 15:09:44 2016
('99% |================================================> |',)
('100%|=================================================>|',)
答案 2 :(得分：0)
我认为这种方式最简单：
items = retrieve_items_from_db
products = items.map do |row|
product = {}
row.each do | k, v|
if k == "Color"
#go do something and add updated key, value pair to products
product[transform_key(k)] = transform_value(v)
else
puts "SKEY:#{k} VALUE: #{v}"
# add k,v to products
product[k] = v
end
end
product
end
您也可以使用Hash :: []将数组对的数组转换为Hash，但对我来说这很笨拙：
items = retrieve_items_from_db
products = items.map do |row|
Hash[row.map do | k, v|
if k == "Color"
#go do something and add updated key, value pair to products
[transform_key(k), transform_value(v)]
else
puts "SKEY:#{k} VALUE: #{v}"
# add k,v to products
[k, v]
end
end]
end