Fast - JSON to CoreData

Question

Fast - JSON to CoreData

I am trying to write the data I receive from JSON to my CoreData. when the app is launched for the first time, I want to receive JSON data and then write it to CoreData and display it in a TableViewCell.

But I couldn't find a way to write JSON to CoreData.

import CoreData
class TableViewCell: UITableViewCell {

    @IBOutlet weak var authorLabel: UILabel!

    var context: NSManagedObjectContext? {
        get {
            let appDel = UIApplication.sharedApplication().delegate as! AppDelegate
            let _context = appDel.managedObjectContext
            return _context
        }
    }

    var author:AuthorList? {
        didSet{
            self.setupAuthor()
        }
    }

    func setupAuthor(){
        var error: NSError?
        let request = NSFetchRequest(entityName: "AuthorList")
        let results = self.context!.executeFetchRequest(request, error: &error) as! [Article]

        if let _error = error {
            println("\(_error.localizedDescription)")
        } 
        self.authorLabel.text = author!.authorName  
    }
}

+3

json ios swift core-data

serdar aylanc June 24. 15 at 19:45

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1 answer

Adrian · Accepted Answer · 2015-06-24T20:46:44+0000

I did it in Objective-C, but I don't have Swift code ready for you. However, I'll post how I did it w / Objective-C and you can "translate" it to Swift. I assume you have the kernel content configured.

In mine, AppDelegate

I added "check" to didFinishLaunchingWithOptions

:

[self seedDataCheck];

At the bottom, I created the following method:

- (void)seedDataCheck {
    // Count what in the managedObjectContext
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"YourEntity"
                                              inManagedObjectContext:self.managedObjectContext];
    [fetchRequest setEntity:entity];

    NSError *error;
    NSUInteger itemsInManagedObjectContext = [self.managedObjectContext countForFetchRequest:fetchRequest error:&error];

    // If nothing there, import JSON
    if (itemsInManagedObjectContext == 0) {
        NSLog(@"AppDelegate.m seedDataCheck: importSeedData called");
        [self importSeedData];
    } else {
        NSLog(@"AppDelegate.m seedDataCheck: No import required");
    }
}

Then I created a separate method to import the seed data:

- (void)importSeedData {
    NSError *error = nil;

    // Ensure a managedObjectContext is instantiated
    if (![self.managedObjectContext save:&error]) {
        NSLog(@"Error while saving %@", ([error localizedDescription] != nil) ? [error localizedDescription] : @"Unknown error");
    } else {
        NSLog(@"self.managedObjectContext = %@", self.managedObjectContext);
    }

    // Create dataPath and put items in an NSArray. Nothing is saved, just exists in memory.
    NSError *err = nil;
    NSString *dataPath = [[NSBundle mainBundle] pathForResource:@"yourJSONData" ofType:@"json"];
    NSLog(@"%@",dataPath);
    NSArray *yourArrayOfJSONStuff = [NSJSONSerialization JSONObjectWithData:[NSData dataWithContentsOfFile:dataPath]
                                                         options:kNilOptions
                                                           error:&err];

    NSLog(@"AppDelegate.m importSeedData: There are %lu items in the array", (unsigned long)stretches.count);

    // Take the array of stuff you just created and dump it in the managedObjectContext
    [yourArrayOfJSONStuff enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        NSManagedObject *yourManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"YourManagedObject"
                                                         inManagedObjectContext:self.managedObjectContext];

        // Link keys from NSArray * yourArrayOfJSONStuff to NSManagedObjects
        yourManagedObject.attribute1 = [obj objectForKey:@"yourAttribute"];
        yourManagedObject.attribute2 = [obj objectForKey:@"yourAttribute2"];
        // blah blah blah

        NSError *error;
        if (![self.managedObjectContext save:&error]) {
            NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
        }
    }];
    NSLog(@"AppDelegate.m importSeedData: Data imported");
}

I'm not sure where you're getting your JSON from, but if it's static somewhere like a spreadsheet, you might find this site useful for getting data to dump JSON files.

http://shancarter.github.io/mr-data-converter/

As far as displaying data in UITableViewCell

, you probably want to customize UITableViewController

and customize your prototype cell to display data from yours managedObjectContext

. This is a pretty "well traveled" path, so I'll make you take a look at this tutorial:

http://www.raywenderlich.com/85578/first-core-data-app-using-swift

Fast - JSON to CoreData

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