Parse.com保存对象一次

Question

I am saving a PFObject called item, into a class called Objects . So the class is Objects , and in that class I have a column called item (which are string objects). Every time a row in my tableView is tapped, the app saves the text of that row to parse.

And if you tap this row 3 times for example, it will save the text 3 different times. Is there a way to only save it once.

Can I use an if statement to check if that string already exists in parse and if so then not save it.

Update:

If I have a class called MenuItem. In MenuItem, I have a string column called item.

Then in my app I have

menuItem[@"item"] = @"item1";
[menuItem saveInBackground];

This code runs every time the app is opened lets say.

How would I check this?

I'm looking at the documentation and I think it is something like this?

   PFQuery *query = [PFQuery queryWithClassName:@"MenuItem"];
[query whereKey:@"item" hasPrefix:@""];
[query findObjectsInBackgroundWithBlock:^(NSArray *items, NSError *error) {


    if (!error) {
        // The find succeeded.
        NSLog(@"Successfully retrieved %lu items.", (unsigned long)items.count);
        // Do something with the found objects
        for (PFObject *item in items) {
            NSLog(@"%@", item.objectId);
        }
    } else {
        // Log details of the failure
        NSLog(@"Error: %@ %@", error, [error userInfo]);
    }


}];

I am just missing the if statement to check it the item is already there?

Thanks

Answer 1

It's a little bit hard to give an exact answer without code, but if i would be in your shoes, i would do this:

a. Version

If you have to save one NSString variable, i would create an Item column inside the User class and save it there. In this way if a user taps the same cell multiple times he will just override the same string again and again.

b. Version

Before you save the string you can query the Objects class and follow some different logics. My opinion is that the easiest way is to loop trough every object that was uploaded by the current user and if the user already has an object with the same string as the current cell has, just don't upload the photo and the user can tap the same cell as many times as he want.

c. Version

Display somehow that the cell was tapped, so the user will know when a cell was tapped. It's not sure that which action uploads the content, if you do it with a button just set different colors for the different states, or if you do it with a cell, just edit the color of the selected cells.

Answer 2

一种实现方法是，编写一个解析查询（PFQuery到item class）以查明用户是否已经被用户点击，如果没有，则用户会将其保存为新对象，否则无需保存再来一次。

Answer 3

This should do it

If you have to save one NSString variable, i would create an Item column inside the User class and save it there. In this way if a user taps the same cell multiple times he will just override the same string again and again.

[saveInBackgroud];

Answer 4

使用后台保存

[parseObject saveInBackgroud];