Ability to revert all changes or a single field on `PFObject`.

[nlutsenko]

After changing a single field on PFObject - there is no functionality to revert it back to the server state, even though we have the server state available internally. This is implemented in dotNet SDK via ParseObject.revert() method which reverts any changes to an object that were done after last successful save/fetch.

Implementation would require:

• Add PFObject.revert() that would clear all operations in operationSetQueue and rebuild estimatedData
• Add PFObject.revertObjectForKey(key: String) that would remove all operations for that key in operationSetQueue as well as rebuild estimatedData.

[mykrr]

I am also facing the same issue as in #51. Please provide us quick fix for this.

[kashif]

so something like:

- (void)revert {
    @synchronized (lock) {
        [operationSetQueue removeAllObjects];
        [self rebuildEstimatedData];
    }
}

-(void)revertObjectForKey:(NSString *)key {
    @synchronized (lock) {
        NSUInteger index = [operationSetQueue indexOfObject:key];
        [operationSetQueue removeObjectAtIndex:index];
        [self rebuildEstimatedData];
    }
}

I can give this issue a go if no one else is doing it...

[nlutsenko]

@kashif pretty close, there are a little bit more things there - availableKeys would need to be adjusted as well as we need to checkpointAllMutableContainers.
Also - operationSetQueue contains PFOperationSet objects, not just keys.

[kashif]

thanks for the info @nlutsenko just about to send a pull request. At the moment I am thinking:

- (void)revert {
    @synchronized (lock) {
        [operationSetQueue removeAllObjects];
        [self rebuildEstimatedData];
        [self checkpointAllMutableContainers];
    }
}

-(void)revertObjectForKey:(NSString *)key {
    @synchronized (lock) {
        NSUInteger index = [operationSetQueue indexOfObject:key];
        [operationSetQueue removeObjectAtIndex:index];
        [_availableKeys removeObject:key];

        PFFieldOperation *changes = [[self unsavedChanges] objectForKey:key];
        index = [operationSetQueue indexOfObject:changes];
        [operationSetQueue removeObjectAtIndex:index];

        [self rebuildEstimatedData];
        [self checkpointAllMutableContainers];
    }
}

[grantland]

Also see https://github.com/ParsePlatform/Parse-SDK-Android/blob/master/Parse/src/main/java/com/parse/ParseObject.java#L842

[kashif]

thanks @grantland having a look

[grantland]

Another optimization that Android should probably have is no-oping if we're not dirty or the key isn't dirty.

[nlutsenko]

Fully done. Thanks everyone.