Currently I am trying to loop through NSArray which contains NSManagedObject.
When I am trying to cast the fetched object its throwing me an error.
Here is the code
for var i = 0; i < self.displayedHistoryListContent.count ; i=i+1{
var productObject: Product = self.displayedHistoryListContent.objectAtIndex(i) as Product
}
Product is my NSManagedObject.
Application crashes at the line where I am doing casting 'as Product'
Can someone tell me where I am going wrong?
Are you sure that the objects in the array are in fact of the class Product? When dealing with NSManagedObject's it is easy to get confused and refer to a set instead of the object itself.
You probably know that a cast is not a conversion?
Use a println() to see wat kind of object is really in there
It really looks like your array does not contain Products only. Try with as? instead of as to confirm this. You can use NSLog to see what is in the array when you expect a Product.
Related
How can i add a queryConstraint on a object?
This is my current code but it returns no objects. I guess my current code is actually to query on arrays and not objects. But I can't find a way to do this for objects.
let query = Device.query()
.where(containsString(key: "apps", substring: "Google"))
This is the database
I recommend looking at the playgrounds to see how to use ParseSwift properly. More specifically, finding objects.
The first problem is apps is an object, which is actually a dictionary. You can’t use a substring constraint on a dictionary or other object. The actual way to do it is:
let objectToFind = [“Google”: “300”]
let query = Device.query("apps" == objectToFind),
I'm trying to create a MutableProperty which holds a Results received from Realm.objects(_:).
To create the property I need to give it an initial value; hence an 'empty' Results.
I've tried creating one using:
var someThings = Results<SomeObject>()
MutableProperty(someThings)
But the compiler gives me the error: Cannot invoke initializer for type 'Results<SomeObject>' with no arguments.
While I understand the error, I'm not really sure how to create a Results object in this context.
Looking at the source of Results I couldn't find an init either.
So my question is; how can I create a Results myself to use in a MutableProperty?
Edit:
I've seen this question...but that doesn't really help (unless I'm going to create a "wrapper" for the MutableProperty or something).
With help of the comments on my OP; I created a mutable property with an empty set of results by fetching objects with an 'invalid' filter.
E.g. MutableProperty(realm.objects(SomeObject.self).filer("EMPTY SET")).
I need some help with my Swift rookie programming...
In a many-to-many relationship, I have a NSManagedObjectID that I`ve segued from another view controller.
To retrive data from it I have used this:
var elevid :NSManagedObjectID?
let person = context.object(with: studentId!)
nameTextField.text = person.value(forKey: "name") as? String
This works fine, but when I try to get an attribute from a relationship I`m stuck.
I´ve tried this:
let isAtSchool = person.value(forKeyPath: "isAtSchool.monday") as! Bool
but I get an error telling me:
Could not cast value of type '__NSSingleObjectSetI' (0x10ac63aa8) to 'NSNumber' (0x109e5a4a8).
If I use ? after as instead of ! it returns nil.
Someone know how to do this?
When you ask for the name property you're asking for a single value, so that's no problem. But when you're using this key path you're traversing a to-many relationship. There could be 2 or 10 or a million related objects, but you you're asking for a single Bool. How is that supposed to work?
It's not clear what you actually want in this situation. Of those potentially millions of related objects, how do you want to calculate the value of that Bool? Probably you want to do something like pick out a single related object out of those (potential) millions and get the Bool from that single instance. But for all I know you might want to scan over all of them and see what the most common Bool value is.
How to change your code depends on what you really need, how that single Bool value should be determined. One way or another you need to get from (potential) millions of related objects to a single Bool-- and you can't do that via a key path lookup.
So long story short, there's a discrepancy between the output of a NSMutableDictionary's contents and the result of calling allValues on the same object. Below is some debugger output after inspecting the object which demonstrates my problem: (made generic of course)
(lldb) po self.someDict.allKeys
<__NSArrayI 0xa5a2e00>(
<SomeObject: 0xa5a2dc0>,
<SomeObject: 0xa5a2de0>
)
(lldb) po self.someDict.allValues
<__NSArrayI 0xa895ca0>(
0.5,
0.5
)
(lldb) po self.someDict
{
"<SomeObject: 0xa5a2dc0>" = (null);
"<SomeObject: 0xa5a2de0>" = (null);
}
So as we can see, the actual output of the NSMutableDictionary contains null values for both its entries, but the contents of .allValues contains the proper data. These three outputs were taken at the same time in execution.
I'm not sure why this is happening, but I think it may have something to do with the fact that I'm encoding/decoding the object which this dictionary is a property of using CoreData. I believe I'm doing this properly:
[aCoder encodeObject:self.someDict forKey:#"someDict"];
and to decode
self.someDict = [aDecoder decodeObjectForKey:#"someDict"];
The weird thing is that if I inspect the dictionary before it ever gets encoded, it is still in the state described at the beginning of the post, so this is why I'm doubtful the CoreData actions are screwing with the contents.
As always, please don't hesitate to request additional information.
EDIT: The problem was as answered below. I was using a custom class which didn't cooperate with isEqual, so my solution was to change the storage and structure of my logic, which made using a Dictionary unnecessary.
I have not been able to duplicate the problem using NSString as keys and NSNumber as values. I suspect that your custom class does not properly implement hash and/or isEqual. Specifically, the results from those two methods must be consistent, meaning that if isEqual returns true, then the hash values for the two objects must be identical.
You also need to ensure that your class implements NSCopying properly and that a copy is equal to the original.
As a general rule, don't use custom objects for dictionary keys. Just use strings and be done with it.
As user3386109 points out, custom objects must properly implement the -hash and -isEqual methods in order to be used as dictionary keys, and even then, custom objects don't work correctly for dictionary keys for things like key/value coding.
Hello.......
in my apps, i have problem with xml parising .i have same tags differentiate with integer value.each tag has different value.
now the problem me facing is accessing this value for that particular tag only.
plz anybody have idea abat this.
let me know.
mean's the problem is that i have one MutableArray and all record in it. and i want to show some values in one view and reaming some value show in another view and reaming in another view..
But the MutableArray is same..
and one more thing is that i want to get tag value
<subject>XYZ</subject>
the output is subject i want.
i do not need of XYZ i need only subject..
sorry i can not show what i want but please understand my question and give me the answer
Thanks
Use NSMutableDictionary instead NSMutableArray.
From documentation.
The NSMutableDictionary class declares the programmatic interface to
objects that manage mutable associations of keys and values. It adds
modification operations to the basic operations it inherits from
NSDictionary.