nspredicate

问题 I have a tableView that has 5 different possible datasources depending on a flag object (NSNumber *)dataSourceAssignment . I've implemented an NSSortDescriptor that sorts dataSource by a (float)confidenceRating . After the datasource is assigned, I need to be able to filter the dataSource array by a (NSString *)genre . I understand how to use NSPredicate to filter my array, but I can't figure out how to do it efficiently when there are 5-6 different genre strings that could be checked. The

问题 I've looked into filtering my data in my app and I got a recommendation to look at NSPredicate. I've been looking into it in one of hte Apress books, but I'm having a problem finding an example so I'm trying to create one. If I had something like this: myObject : NSObject @property (nonatomic, retain) NSString *firstName; @property (nonatomic, retain) NSString *lastName; @property (nonatomic, assign) NSInteger age; create some objects and put then into an array. Then I'm not sure how I would

问题 I'm stuck in a problem with my Core Data model and a fetch request that involves dates. I have some objects in a entity with a NSDate attribute; I need to extract the objects with the date of today but I always get nil from this code: public func getObjectsOfToday() -> Array<myObject>? { let entityDescription = NSEntityDescription.entityForName("Objects", inManagedObjectContext: DataAccess.sharedInstance.managedObjectContext) let request = NSFetchRequest() request.entity = entityDescription

问题 Is there a shorter way to write the format string for a predicate equivalent to this: [NSPredicate predicateWithFormat: @"key1 CONTAINS[cd] %@ OR key2 CONTAINS[cd] %@ OR key3 CONTAINS[cd] %@", searchString, searchString, searchString]; I have written a few predicate format strings like this, and I was thinking to simplify that by writing a method that takes an array of key paths and the search string to construct such a predicate. But I thought I’d ask if there is a built-in way to do this,

问题 If I have 2 strings: "My name is Eric" "America is great" And my substring is 'eri'. How can I write a function that will only return true for the first sentence, because it has a WORD that starts with eri (Eric) and does not just contain eri (AmERIca). Note; I have been using NSPredicates, but using CONTAINS would return both, and using BEGINSWITH would only check the first word. This string is also contained in an Object, say and the property is called , so my current code is: NSPredicate

问题 I have some pretty interesting logic going, basically I have this data which I want to check over before I display the next view.. just in case the data is empty I want to pop the view, if the data is not empty then I want to load the the view to display it onto the navigational stack. so in my tableView:didSelectRowAtIndexPath: method, when the selection is made I, get the current selection ID number so I can restrict the values of the data Im going to parse to only related values. This is

问题 I'm saving CLPlacemark in Core data using NSValueTransformer . (so it's saved as NSData ) However I've come to a point where I need to filter the saved objects based on another CLPlacemark object. I've tried this, it doesn't work: NSExpression *exprPath = [NSExpression expressionForKeyPath:@"placemark"]; NSExpression *exprKeyword = [NSExpression expressionForConstantValue:[NSKeyedArchiver archivedDataWithRootObject:placemark]]; NSPredicate *predicate = [NSComparisonPredicate

问题 I have a Core Data project and am having difficulty searching the data with a simple calculated field and have no idea why it's not working. I have a Tutor entity, with core data string attributes "tutorFirstName" and "tutorLastName". I've created an additional string attribute "tutorFullName" which is populated in a Category as such: NSString *fullName = [@[self.tutorFirstName, self.tutorLastName] componentsJoinedByString:@" "]; The data is populated fine, but when I perform the following

问题 I am looking at the following type of data structure: { author = "Author 1"; channelIds = ( 7 ); }, { author = "Author 2"; channelIds = ( 7, 1 ); }, , { author = "Author 3"; channelIds = ( 3, 7 ); } I'd like to build an array consisting of all items where channeldIds = 7 . I was trying things along the lines of the following predicate: NSPredicate * filterById = [NSPredicate predicateWithFormat:@"channelIds[0] = '7'"]; How can I do what I'd like here? I can have an x number of channelIds, is

问题 I want to check string with regex in Objective c. My code NSString *regexAmazonOrder =@"[a-zA-Z0-9]*"; NSPredicate *predicateAmazonOrder = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",regexAmazonOrder]; if([predicateAmazonOrder evaluateWithObject:cardNumber.text]) { NSLog(@"Its coming inside AMAZON ORDER EVALUATIONS"); ... } But its not working. Help me out. I know its simple but eating my mind!!! Thanks 回答1: Try like this: (Untested, just to give you an starter) NSError *error = NULL;