iphone - 优化 objective-c 代码以访问联系人

Question

我有一些代码可以从Addreesbook复制联系人。如果联系人数量少，它会完美地工作。现在，在我的手机中，我们有1200个联系人，当我尝试复制它们时，应用程序崩溃了。谁能帮助我优化此代码或重写代码？我使用的代码添加如下:

ABAddressBookRef addressBook = ABAddressBookCreate();
    CFArrayRef allPeople = ABAddressBookCopyArrayOfAllPeople(addressBook);
    CFIndex nPeople = ABAddressBookGetPersonCount(addressBook);

    NSString *requestContactsString = @"<contacts>";    


    for (int i=0; i<nPeople; i++)
    {
        NSLog(@"Started : %d", i);

        ABRecordRef ref = CFArrayGetValueAtIndex(allPeople, i);
        CFTypeRef firstName = ABRecordCopyValue(ref, kABPersonFirstNameProperty);
        CFTypeRef lastName = ABRecordCopyValue(ref, kABPersonLastNameProperty);
        CFTypeRef email = ABRecordCopyValue(ref, kABPersonEmailProperty);
        CFTypeRef phone = ABRecordCopyValue(ref, kABPersonPhoneProperty);

        requestContactsString = [requestContactsString stringByAppendingFormat:@"<item>"];

        if(firstName)
        {
            requestContactsString = [requestContactsString stringByAppendingFormat:@"<firstname>%@</firstname>", firstName];
            CFRelease(firstName);
            firstName = nil;
        }
        if(lastName)
        {
            requestContactsString = [requestContactsString stringByAppendingFormat:@"<lastname>%@</lastname>", lastName];
            CFRelease(lastName);
            lastName = nil;
        }
        if(email)
        {
            if(ABMultiValueGetCount(email)>0)
            {
                CFTypeRef em = ABMultiValueCopyValueAtIndex(email, 0);
                requestContactsString = [requestContactsString stringByAppendingFormat:@"<email>%@</email>", em];
                CFRelease(em);
            }
            CFRelease(email);
            email = nil;
        }
        if(phone)
        {
            if(ABMultiValueGetCount(phone)>0)
            {
                CFTypeRef ph = ABMultiValueCopyValueAtIndex(phone, 0);
                requestContactsString = [requestContactsString stringByAppendingFormat:@"<phone>%@</phone>", ph];
                CFRelease(ph);
            }
            CFRelease(phone);
            phone = nil;
        }

        requestContactsString = [requestContactsString stringByAppendingFormat:@"</item>"];
    }


    if(allPeople)
    {
        CFRelease(allPeople);
        allPeople = nil;
    }
    if(addressBook)
    {
        CFRelease(addressBook);
        addressBook = nil;
    }

    requestContactsString = [requestContactsString stringByAppendingFormat:@"</contacts>"];

    NSString *hashedContactsString = [self generateHashedPassword:requestContactsString];

Answer 1

我看到的主要低效率是使用[NSString stringByAppendingFormat]，每次调用它时都会创建一个新的NSString对象。这意味着您有大量的长自动释放的NSString对象，这些对象将在下一个运行循环之前不再使用(除非您使用的是ARC，在这种情况下情况可能会更好)。

我认为您可以通过将requestContactsString设置为NSMutableString并使用[NSMutableString appendString](reference)来更好地利用内存并获得更好的性能。这将修改现有对象，分配更多内存以接受新字符串。

每个追加看起来像这样:

[requestContactsString appendString:[NSString stringWithFormat:@"<lastname>%@</lastname>", lastName]];

仍然会创建大量自动释放的对象，但是它们的小很多。