Ios 核心数据获取记录按关系分组？

我有两个实体，分别名为

费用

和

费用分类

，

费用

与

类别费用

具有以下属性- 名称支出类别，目的地-支出分类，反向-支出。

ExpensesCategory

有一个名为expenseCography的字符串类型属性，而

Expenses

有一个名为amount的属性。 现在，我想获取按开支类别分组的开支，其金额为总和。 这是我的密码

NSSortDescriptor *sortTitle =[NSSortDescriptor sortDescriptorWithKey:@"addedTimestamp"
                                                               ascending:YES];
    NSArray *sortDescriptors = [NSArray arrayWithObjects:sortTitle, nil];
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Expense"
                                              inManagedObjectContext:context];

    NSPredicate *predicate;
    predicate =[NSPredicate predicateWithFormat:@"(addedTimestamp <= %@) AND (addedTimestamp >= %@)",currentDate, endDate];
        NSAttributeDescription* amtDescription = [entity.attributesByName objectForKey:@"amount"];
        NSRelationshipDescription* nameDesc = [entity.relationshipsByName objectForKey:@"expenseCategory"];

        NSExpression *keyPathExpression = [NSExpression expressionForKeyPath: @"amount"];
        NSExpression *countExpression = [NSExpression expressionForFunction: @"sum:"
                                                                  arguments: [NSArray arrayWithObject:keyPathExpression]];
        NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
        [expressionDescription setName: @"Sum"];
        [expressionDescription setExpression: countExpression];
        [expressionDescription setExpressionResultType: NSDecimalAttributeType];

        [fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:amtDescription, expressionDescription, nameDesc, nil]];
        [fetchRequest setPropertiesToGroupBy:[NSArray arrayWithObject:nameDesc]];
        [fetchRequest setResultType:NSDictionaryResultType];

        [fetchRequest setEntity:entity];
        [fetchRequest setPredicate:predicate];
        [fetchRequest setSortDescriptors:sortDescriptors];
    [context executeFetchRequest:fetchRequest error:&error];

NSSortDescriptor*sortTitle=[NSSortDescriptor sortdescriptor with key:@“addedTimestamp”
上升：是]；
NSArray*sortDescriptors=[NSArray数组及其对象：sortTitle，nil]；
NSFetchRequest*fetchRequest=[[NSFetchRequest alloc]init]；
NSEntityDescription*实体=[NSEntityDescription entityForName:@“费用”
inManagedObjectContext:context]；
NSPredicate*谓词；
谓词=[NSPredicate谓词格式：@“（addedTimestamp=%@）”，currentDate，endDate]；
NSAttributeDescription*amtDescription=[entity.attributesByName objectForKey:@“金额”]；
nsrrelationshipsdescription*nameDesc=[entity.relationshipsByName objectForKey:@“ExpenseCegory”]；
NSExpression*keypath表达式=[NSExpression表达式forkeypath:@“amount”]；
NSExpression*countExpression=[NSExpression expressionForFunction:@“sum:”
参数：[NSArray arrayWithObject:keyPathExpression]]；
NSExpressionDescription*expressionDescription=[[NSExpressionDescription alloc]init]；
[expressionDescription setName:@“Sum”]；
[expressionDescription setExpression:countExpression]；
[expressionDescription setExpressionResultType:NSDecimalAttributeType]；
[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:amtDescription，expressionDescription，NameDescription，nil]]；
[fetchRequest setPropertiesToGroupBy:[NSArray arrayWithObject:nameDesc]]；
[fetchRequest setResultType:NSDictionaryResultType]；
[FetchRequestSetEntity:entity]；
[FetchRequestSetPredicate:谓词]；
[FetchRequestSetSortDescriptors:sortDescriptors]；
[context executeFetchRequest:fetchRequest错误：&错误]；

但当我运行时，由于未捕获的异常“NSInvalidArgumentException”，我得到了终止应用程序的

，原因：“传递给setPropertiesToFetch的属性/关系描述名称：必须与fetch实体上的名称匹配

任何帮助都将不胜感激。

您应该看看这项技术。在此url中，您可以找到

员工

和

部门

之间的示例

希望有帮助

你应该看看这个技巧。在此url中，您可以找到

员工

和

部门

之间的示例

---

希望有帮助

您正在将

|expressionDescription |

传递到

setPropertiesToFetch:

，这是一个

NSExpressionDescription

setPropertiesToFetch:

只接受

NSPropertyDescriptions

的数组，因此引发异常

---

但是，

setPropertiesToGroupBy:

中允许使用

NSExpressionDescription

和

NSPropertyDescription

。

setPropertiesToFetch:

将

表达式描述

传递给

setPropertiesToFetch:

setPropertiesToFetch:

只接受

NSPropertyDescriptions

的数组，因此引发异常

---

setPropertiesToGroupBy:

中同时允许

NSExpressionDescriptions

和

NSPropertyDescriptions

。

以下是您问题的答案

NSEntityDescription *entity = [NSEntityDescription entityForName:@"ExpenseCategory" inManagedObjectContext:context];

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:entity];

NSError *error;

fetchRequest.predicate =[NSPredicate predicateWithFormat:@"(addedTimestamp <= %@) AND (addedTimestamp >= %@)",currentDate, endDate];

NSSortDescriptor *sortTitle =[NSSortDescriptor sortDescriptorWithKey:@"addedTimestamp" ascending:YES];
fetchRequest.sortDescriptors  = [NSArray arrayWithObjects:sortTitle, nil];

NSExpressionDescription *ex = [[NSExpressionDescription alloc] init];
[ex setExpression:[NSExpression expressionWithFormat:@"@sum.expense.amount"]];
[ex setName:@"Sum"];
[ex setExpressionResultType:NSDecimalAttributeType];

[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"expenseCategory", ex, nil]];
[fetchRequest setPropertiesToGroupBy:[NSArray arrayWithObject:@"expenseCategory"]];
[fetchRequest setResultType:NSDictionaryResultType ];

// Execute the fetch.
NSArray *matchingObjects = [context executeFetchRequest:fetchRequest error:&error];
if ([matchingObjects lastObject]) {
    for (id expenseCategory in matchingObjects) {
        NSLog(@"%@", expenseCategory);
    }
}

NSEntityDescription*entity=[NSEntityDescription entityForName:@“ExpenseControle”inManagedObjectContext:context]；
NSFetchRequest*fetchRequest=[[NSFetchRequest alloc]init]；
[FetchRequestSetEntity:entity]；
n错误*错误；
fetchRequest.predicate=[NSPredicate predicateWithFormat:@“（addedTimestamp=%@）”，currentDate，endDate]；
NSSortDescriptor*sortTitle=[NSSortDescriptor SortDescriptor With Key:@“addedTimestamp”升序：是]；
fetchRequest.sortDescriptors=[NSArray arrayWithObjects:sortTitle，nil]；
NSExpressionDescription*ex=[[NSExpressionDescription alloc]init]；
[ex setExpression:[N表达式表达式格式：@“@sum.expense.amount”]；
[ex setName:@“Sum”]；
[ex setExpressionResultType:NSDecimalAttribute类型]；
[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@“ExpenseCegory”，例如，无]]；
[fetchRequest setPropertiesToGroupBy:[NSArray arrayWithObject:@“ExpenseCography”]；
[fetchRequest setResultType:NSDictionaryResultType]；
//执行提取。
NSArray*matchingObjects=[context executeFetchRequest:fetchRequest错误：&error]；
如果（[matchingObjects s lastObject]）{
用于（匹配对象中的id费用类别）{
NSLog（@“%@”，费用类别）；
}
}

如果要按Expense addedTime而不是ExpenseControle addedTime进行筛选，请将谓词更改为：

fetchRequest.predicate =[NSPredicate predicateWithFormat:@"(expense.addedTimestamp <= %@) AND (expense.addedTimestamp >= %@)",currentDate, endDate];

fetchRequest.predicate=[NSPredicate predicateWithFormat:@“（expense.addedTimestamp=%@）”，currentDate，endDate]；

以下是您问题的答案

NSEntityDescription *entity = [NSEntityDescription entityForName:@"ExpenseCategory" inManagedObjectContext:context];

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
[fetchRequest setEntity:entity];

NSError *error;

fetchRequest.predicate =[NSPredicate predicateWithFormat:@"(addedTimestamp <= %@) AND (addedTimestamp >= %@)",currentDate, endDate];

NSSortDescriptor *sortTitle =[NSSortDescriptor sortDescriptorWithKey:@"addedTimestamp" ascending:YES];
fetchRequest.sortDescriptors  = [NSArray arrayWithObjects:sortTitle, nil];

NSExpressionDescription *ex = [[NSExpressionDescription alloc] init];
[ex setExpression:[NSExpression expressionWithFormat:@"@sum.expense.amount"]];
[ex setName:@"Sum"];
[ex setExpressionResultType:NSDecimalAttributeType];

[fetchRequest setPropertiesToFetch:[NSArray arrayWithObjects:@"expenseCategory", ex, nil]];
[fetchRequest setPropertiesToGroupBy:[NSArray arrayWithObject:@"expenseCategory"]];
[fetchRequest setResultType:NSDictionaryResultType ];

// Execute the fetch.
NSArray *matchingObjects = [context executeFetchRequest:fetchRequest error:&error];
if ([matchingObjects lastObject]) {
    for (id expenseCategory in matchingObjects) {
        NSLog(@"%@", expenseCategory);
    }
}

NSEntityDescription*entity=[NSEntityDescription entityForName:@“ExpenseControle”inManagedObjectContext:context]；
NSFetchRequest*fetchRequest=[[NSFetchRequest alloc]init]；
[FetchRequestSetEntity:entity]；
n错误*错误；
fetchRequest.predicate=[NSPredicate predicateWithFormat:@“（addedTimestamp=%@）”，currentDate，endDate]；
NSSortDescriptor*sortTitle=[NSSortDescriptor SortDescriptor With Key:@“addedTimestamp”升序：是]；
fetchRequest.sortDescriptors=[NSArray arrayWithObjects:sortTitle，nil]；
NSExpressionDescription*ex=[[NSExpressionDescription]