问题
I have created a PFObject named UserInfo. Everything saves to Parse correctly, but when I go to retrieve it I keep getting errors. Here is my code below.
PFQuery *query = [PFQuery queryWithClassName:@"UserInfo"];
[query whereKey:@"user" equalTo:currentUser];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (error) {
NSLog(@"Error: %@ %@", error, [error userInfo]);
} else {
self.userInfo = objects;
NSLog(@"%@", self.userInfo);
self.locationDisplay.text = [self.userInfo valueForKey:@"location"];
}
}];
The NSLog out put for the error is as follows:
-[__NSArrayI length]: unrecognized selector sent to instance 0x9aa2be0
Thank you for the help in advance!
回答1:
The query findObjectsInBackgroundWithBLock: stores an array in objects.
Once this is done, you set your attribute userInfo to point to this array with the line
self.userInfo = objects;
So basically here, self.userInfo holds a reference to an array.
When you try to set your label, you call the method valueForKey: directly on the array. I believe you want to call this method on an object inside this array.
What you could try is change the line to :
self.locationDisplay.text = [[self.userInfo firstObject] valueForKey:@"location"];
which will look for the value for the key @"location" on the first object of your array, which should be a PFObject.
Note : you should first test that objects is not an empty array before calling this line, otherwise you may try to call valueForKey: on a nil object, if the array is empty.
来源：https://stackoverflow.com/questions/25142060/setting-pfobject-in-to-uilabel