Lets say I have an NSArrayController which contains items each with netCost and netProfit properties and I want to create a Total Percent Profit label (containing the sum of the profits divided by the sum of the costs).Lets say I have an NSArrayController which cont
阅读背景：
将NSArrayController中项的属性的聚合设置为从属键
来源：互联网
分享到：
