Question

我正在尝试获取Core Data中托管对象的属性的总和，但似乎无论我做什么我得到0。

我试图获取所有Opportunity对象上的estimatedValue属性的总和。 estimatedValue属性是Core Data中的小数。

这是我当前的代码版本：

[{
    sumOfEstimatedValue = 0;
}]

上述代码的结果是：

[<Opportunity: 0x60800009dd80> (entity: Opportunity; id: 0x60800002d8c0 <x-coredata:///Opportunity/tB6E74585-FDA0-4061-89CC-D89EEB25156C17> ; data: {
    company = nil;
    contact = "0x608000028d40 <x-coredata:///Contact/tB6E74585-FDA0-4061-89CC-D89EEB25156C2>";
    createdDate = "2017-09-03 22:40:00 +0000";
    estimatedValue = "42.41";
    opportunityDescription = nil;
    projectedCloseDate = nil;
    stage = "0x60800002d860 <x-coredata:///Stage/tB6E74585-FDA0-4061-89CC-D89EEB25156C16>";
}), <Opportunity: 0x60800009dc90> (entity: Opportunity; id: 0x60800002d380 <x-coredata:///Opportunity/tB6E74585-FDA0-4061-89CC-D89EEB25156C15> ; data: {
    company = nil;
    contact = "0x608000028d40 <x-coredata:///Contact/tB6E74585-FDA0-4061-89CC-D89EEB25156C2>";
    createdDate = "2017-09-03 22:40:00 +0000";
    estimatedValue = "42.41";
    opportunityDescription = nil;
    projectedCloseDate = nil;
    stage = "0x60800002d440 <x-coredata:///Stage/tB6E74585-FDA0-4061-89CC-D89EEB25156C14>";
}), <Opportunity: 0x60800009d9c0> (entity: Opportunity; id: 0x60800002b8e0 <x-coredata:///Opportunity/tB6E74585-FDA0-4061-89CC-D89EEB25156C9> ; data: {
    company = nil;
    contact = "0x608000028d40 <x-coredata:///Contact/tB6E74585-FDA0-4061-89CC-D89EEB25156C2>";
    createdDate = "2017-09-03 22:40:00 +0000";
    estimatedValue = "42.41";
    opportunityDescription = nil;
    projectedCloseDate = nil;
    stage = "0x60800002aaa0 <x-coredata:///Stage/tB6E74585-FDA0-4061-89CC-D89EEB25156C8>";
}), <Opportunity: 0x60800009dab0> (entity: Opportunity; id: 0x60800002c580 <x-coredata:///Opportunity/tB6E74585-FDA0-4061-89CC-D89EEB25156C11> ; data: {
    company = nil;
    contact = "0x608000028d40 <x-coredata:///Contact/tB6E74585-FDA0-4061-89CC-D89EEB25156C2>";
    createdDate = "2017-09-03 22:40:00 +0000";
    estimatedValue = "42.41";
    opportunityDescription = nil;
    projectedCloseDate = nil;
    stage = "0x60800002d3e0 <x-coredata:///Stage/tB6E74585-FDA0-4061-89CC-D89EEB25156C10>";
}), <Opportunity: 0x60800009dba0> (entity: Opportunity; id: 0x60800002d140 <x-coredata:///Opportunity/tB6E74585-FDA0-4061-89CC-D89EEB25156C13> ; data: {
    company = nil;
    contact = "0x608000028d40 <x-coredata:///Contact/tB6E74585-FDA0-4061-89CC-D89EEB25156C2>";
    createdDate = "2017-09-03 22:40:00 +0000";
    estimatedValue = "42.41";
    opportunityDescription = nil;
    projectedCloseDate = nil;
    stage = "0x60800002c140 <x-coredata:///Stage/tB6E74585-FDA0-4061-89CC-D89EEB25156C12>";
}), <Opportunity: 0x60800009d3d0> (entity: Opportunity; id: 0x60800002b3a0 <x-coredata:///Opportunity/tB6E74585-FDA0-4061-89CC-D89EEB25156C7> ; data: {
    company = nil;
    contact = "0x608000028d40 <x-coredata:///Contact/tB6E74585-FDA0-4061-89CC-D89EEB25156C2>";
    createdDate = "2017-09-03 22:40:00 +0000";
    estimatedValue = "42.41";
    opportunityDescription = nil;
    projectedCloseDate = nil;
    stage = "0x60800002abe0 <x-coredata:///Stage/tB6E74585-FDA0-4061-89CC-D89EEB25156C6>";
})]

以下是打印应用中保存的商机的信息：

{{1}}

感谢您提供的任何帮助。

Answer 1

核心数据不支持您尝试执行的表达。

来自Apple Docs：

Core Data不支持聚合表达式。

来源：https://developer.apple.com/documentation/foundation/nsexpression

相反，您应该在执行提取后对所有实体求和。

Answer 2

原始问题中的代码现在正在运行。我不太确定出了什么问题，但是从我的设备上擦除应用数据并使用完全相同的数据填充它来固定它。

Swift 3核心数据NSExpression总是返回0

2 个答案: