密钥< transientproperty>在实体中找不到 [英] Keypath <transientproperty> not found in entity

问题描述

我想在表视图的section标题中显示一个格式化的日期。

I want to show a formatted date in the section header of a table view..

我使用下面的代码，但它抛出一个异常 ***由于未捕获异常NSInvalidArgumentException而终止应用程序，原因：'keypath dateSectionIdentifier在实体中找不到< NSSQLEntity费用id = 1>'。

I used the following code.but its throwing an exception *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'keypath dateSectionIdentifier not found in entity <NSSQLEntity Expense id=1>'.

猜测在添加排序描述符时会出现异常。

guess the exception is coming when adding a sort descriptor.

NSMutableArray *sortDescriptors = [[NSMutableArray alloc] initWithCapacity:20];
NSSortDescriptor *mainSortDescriptor = [[NSSortDescriptor alloc] initWithKey:dateSectionIdentifier ascending:NO];
[sortDescriptors addObject:mainSortDescriptor];
[fetchRequest setSortDescriptors:sortDescriptors];

// Expense.h

//Expense.h

NSString *dateSectionIdentifier;

// Expense.m

//Expense.m

@dynamic dateSectionIdentifier

-(NSString *)dateSectionIdentifier{
[self willAccessValueForKey:@"dateSectionIdentifier"];
NSString *tempDate = [self primitiveDateSectionIdentifier];
[self didAccessValueForKey:@"dateSectionIdentifier"];
if(!tempDate){
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
    [dateFormatter setDateFormat:@"d MMMM yyyy"];
    tempDate = [dateFormatter stringFromDate:[self date]];
    [self setPrimitiveDateSectionIdentifier:tempDate];
    [dateFormatter release];
}
return tempDate;

}

推荐答案

的问题表明dateSectionIdentifier是一个临时的属性。

The title of your question indicates that "dateSectionIdentifier" is a transient property.

您不能在排序描述符中使用transient属性）的核心数据提取请求，如果SQLite用作存储类型。这是一个记录的限制，只能使用持久属性。

You cannot use a transient property in a sort descriptor (or in a predicate) of a Core Data fetch request if SQLite is used as store type. That is a documented restriction, only persistent properties can be used.

请参阅持久存储类型和行为。

这篇关于密钥< transientproperty>在实体中找不到的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！