a=[{id:1,sum:11},{id:2,sum:22}]
语法格式：
a.each/map/inject/collect {|a| ...代码块...}
a.each/map/inject/collect do |a|
...代码块...
end
each：遍历数据a，对原数组进行处理
b=a.each do |a|
a[:sum]=11
end
b=[{id:1,sum:11},{id:2,sum:11}]
a=[{id:1,sum:11},{id:2,sum:11}]
map：遍历数据a，不对原数组进行处理，创建新数组
b=a.map do |a|
a[:sum]=11
end
b=[{id:1,sum:11},{id:2,sum:11}]
a=[{id:1,sum:11},{id:2,sum:22}]
collect:同map
