Nspredicate example relationship letters

objective c - NSPredicate case-insensitive matching on to-many relationship - Stack Overflow

nspredicate example relationship letters

However, I didn't mention relationships in that discussion. This means that the predicate format string of our example evaluates to last == "Doe". Let's fetch every Person record whose name CONTAINS the letter j. returns the sum of the objects in the collection based on the property. [ NSPredicate predicateWithFormat: @"[email protected] Comparison of NSPredicate and Spotlight Query Strings · Spotlight and Predicate Format String Syntax BNF Definition of Cocoa Predicates.

More Fetching and Deleting Managed Objects With Core Data

Instead of writing the following: Structuring Your Data In some situations, there may be tension between the representation of your data and the use of predicates. If you intend to use predicates in your application, the pattern of typical query operations may influence how you structure your data.

nspredicate example relationship letters

In Core Data, although you specify entities and entity-class mapping, the levels that create the underlying structures in the persistent store are opaque. Nevertheless, you still have control over your entities and the properties they have. In addition to tending to be expensive, joins may also restrict flexibility. It may be appropriate, therefore, to de-normalize your data.

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In general—assuming that queries are issued often—it may be a good trade-off to have larger objects, but for it to be easier to find the right ones and so have fewer in memory. You can set the predicate in code using setFilterPredicate: The object that implements the method may be the File's Owner or another controller object. Note that we mark some of the item records as completed by setting their completed attribute to true. We also set the list relationship of each item record to the current list record.

We push the changes to the persistent store by saving the managed object context and we set didSeedPersistentStore to true in the user defaults database.

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If your application takes too long to launch, the operating system's watchdog kills your application. The watchdog has no mercy. Sorting Records The order of the records returned by a fetch request is undefined.

ios - Hello, I need to filter a list of contacts but NSPredicate don't work - Stack Overflow

The users of your application expect more from you, though. Sorting records is a common task. To sort the records returned by the fetch request, we add a sort descriptor, an instance of the NSSortDescriptor class. We initialize it by invoking its init key: We then set the sortDescriptors property of the fetch request.

The sortDescriptors property is of type [NSSortDescriptor], which means we can combine multiple sort descriptors. The order of the sort descriptors determines in which order the sort descriptors are applied. We execute the fetch request and print the names of the records to the console.

More Fetching and Deleting Managed Objects With Core Data

Home Leisure Work Predicates We can use predicates to refine the result of a fetch request. Predicates, instances of the NSPredicate class, enable us to specify which records we are interested in. Update the previous example as shown below. The syntax of the predicate is reminiscent of SQL.

nspredicate example relationship letters

The [c] specifier indicates that the case of the letter o should be ignored. This is what the result looks like in the console.

nspredicate example relationship letters

Home Work Predicates also work great with relationships.