我有一个通用方法,如下所示:
-(NSArray *) db_select: (NSString *) entity where: (NSString*) fieldKey equals: (NSString*) value withSortField: (NSString *) sortField withFetchLimits:(NSRange) fetchLimits{
// convert value to a number if it isn't a string
if (value != nil && ![value isKindOfClass:[NSString class]]){
if ([value isKindOfClass:[NSNumber class]]){
value = [((NSNumber*)value) stringValue];
}
}
// assemble
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:entity inManagedObjectContext:moContext];
if (fieldKey != nil){
NSPredicate *predicate = [NSPredicate
predicateWithFormat:@"%K like %@",
fieldKey,value];
[request setPredicate:predicate];
}
[request setEntity:entity];
[request setFetchLimit:fetchLimits.length];
[request setFetchOffset:fetchLimits.location];
if (sortField != nil){
NSSortDescriptor *sortDescriptor = nil;
if (/*TODO fieldKey refers to an NSString */YES){
sortDescriptor = [[NSSortDescriptor alloc] initWithKey:[self extractSortField:sortField] ascending:[self isAscending:sortField] selector:@selector(localizedCaseInsensitiveCompare:)];
} else {
sortDescriptor = [[NSSortDescriptor alloc] initWithKey:[self extractSortField:sortField] ascending:[self isAscending:sortField]];
}
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[request setSortDescriptors:sortDescriptors];
}
// make the request
NSError *error;
return [moContext executeFetchRequest:request error:&error];
}
如果字段(aka fieldKey)不是字符串,则我不想执行localizedCaseInsensitiveCompare。如何查询核心数据架构并确定entity.fieldKey是否为字符串?
谢谢!
最佳答案
您可以通过其实体作为实例:
NSEntityDescription *desc = [myEntity entity];
NSAttributeDescription *attDesc = [[desc propertiesByName] valueForKey:@"myProperty"];
NSAttributeType *type = [attDesc attributeType];
从那里开始,一个简单的开关将确定您要处理的内容。
关于iphone - 查询核心数据属性的类型,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/8176666/