swift - Fetch last record of Entities NSSet? -


i have pet entities can have multiple events:

public class pet: nsmanagedobject {      @nsmanaged var dbname: string     @nsmanaged var events: nsset?    // 1-to-many relationship events }  public class event: nsmanagedobject {     @nsmanaged var key: string     @nsmanaged var date: int64 }

i've set events indexed based on date. i've made function returns events given pet.

func fetcheventsforpet(pet: string) -> [event]? {     let request = nsfetchrequest<nsfetchrequestresult>(entityname: pet.entityname)     let predicate = nspredicate(format: "dbname == %@", pet)     request.predicate = predicate     request.fetchlimit = 1     {         let result = try self.fetch(request) as? [pet]         if let pets = result {             pet in pets {                 if let events = pet.events {                     if let evts = events.allobjects as? [event] {                         return evts                      // return pets events                     }                 }             }         }     } catch {}     return nil }

how modify function return last event (the lastest event based on date)? have fetch events each time or there faster way this?

your entity class definitions imply not have inverse relationship event pet. should create 1 (there very, few occasions better off without inverse). can fetch events directly, rather fetching pets , using events relationship. assuming name inverse relationship "pet", use predicate this:

  let predicate = nspredicate(format: "pet.dbname == %@", pet)

you can apply sort descriptors , fetch limit return recent event given pet name.


Comments

Post a Comment

Popular posts from this blog

How to understand 2 main() functions after using uftrace to profile the C++ program? -

i trying uftrace profile following simple c++ program: #include <iostream> class { public: a() {std::cout << "a created" << std::endl;} ~a() {std::cout << "a destroyed" << std::endl;} }; int main() { a; return 0; } the profile result this: # uftrace a.out created destroyed # duration tid function 2.026 [ 4828] | __cxa_atexit(); [ 4828] | main() { [ 4828] | __static_initialization_and_destruction_0() { 89.397 [ 4828] | std::ios_base::init::init(); 0.768 [ 4828] | __cxa_atexit(); 93.029 [ 4828] | } /* __static_initialization_and_destruction_0 */ 94.425 [ 4828] | } /* main */ [ 4828] | main() { [ 4828] | a::a() { 11.104 [ 4828] | std::operator <<(); 10.825 [ 4828] | std::basic_ostream::operator <<(); 24.514 [ 4828] | } /* a::a */ [ 4828] | a::~a() { 0.978 [ 4828] | ...
Read more

c# - Update a combobox from a presenter (MVP) -

i using mvp in project, new in mvp. have 2 comboboxes. when select option in combobox, combobox should filled new data. this action in presenter. view 'view1' in presenter, , introduced combobox1 , combobox2 properties in 'view1', because need 'datasource', 'displaymember', 'valuemember' , 'refresh()' in method below. but, when using pattern, enough send property like public string combobox2 { { return combobox1.selectedvalue.tosstring(); } } into presenter not whole combobox. how can solve problem? public void onselectedindexchangedcombobox1() { if (view1.combobox1.selectedindex == -1) { return; } datatable dt = tools.getdatatable("a path"); var query = (from o in dt.asenumerable() o.field<string>("afield") == farmerview.combobox1.selectedvalue.tostring() orderby o.field<string>("anotherfield") select...
Read more

How to put a lock and transaction on table using spring 4 or above using jdbcTemplate and annotations like @Transactional? -

i trying put lock on table while writing on table , if happened in between roll-back . trying convert below code lock table test_g1 read; lock table test_g write; -- begin; start transaction; insert test_g1 values(143); insert test_g values(145); select * test_g1; select * test_g; rollback; select * test_g; unlock tables; how convert above code @transactional spring jdbctemplate code? @transactional(rollbackfor={dataaccessexception.class}) public void test(){ jdbctemplate.execute("insert test1 (id, nam) values (4, 'a')"); throw new dataaccessexception("error") { }; } here trying throw error, insert statement should rollback it's not happening . thanks edit-1 attaching code , doing in jdbcdaoimpl.java , mentioned problem comment above test() . app.java package com.cgiri.javabrains.spring4; import org.springframework.beans.factory.annotation.autowired; import org.springframework.context.applic...
Read more