My brain is failing me today. I know this has got to be a simple one, but I just don't see it.
CGFloat *minutes = [self.displayData objectForKey:index];
Incompatible integer to pointer conversion sending 'NSUInteger' (aka 'unsigned int') to parameter of type 'id'
index is a NSUInteger in a loop, (0 1 2 3 etc)
How do I get past this one? Thanks.
The dictionary waits for an object as the key (id) rather than a plain integer (NSUInteger).
Try wrapping the integer in a NSNumber object.
CGFloat *minutes = [self.displayData objectForKey:[NSNumber numberWithUnsignedInteger:index]];
The -objectForKey: method returns a value of type id, but you're trying to assign that to a CGFloat*, which isn't compatible with id because CGFloat isn't a class. If you know that the object you're retrieving from the dictionary is a certain type, say an NSNumber, you can take steps to convert it to a CGFloat when you get it.
Also, you're trying to use an int as a key into a dictionary, but dictionaries require their keys to be objects too. If you want to access your objects by index, store them in an array instead of a dictionary.
Putting it all together, you'd have something like this:
// after changing the displayData to an array
NSNumber *number = [self.displayData objectAtIndex:index];
CGFloat minutes = [number floatValue];
You should not be using a pointer like this:
CGFloat minutes = [self.displayData objectForKey:index];
Easy question. Just don't use NSUIntegrer. Instead of it, do the following:
id index;//then set the index
Related
CGFloat color = [[myArray objectAtIndex:0]valueForKey:#"redComponent"];
I know this array will return a float but xcode is saying:
Initializing 'CGFloat' (aka 'float') with an expression of incompatible type 'id _Nullable'. I have NSLog'd the result even to check it. How do i get over this?
objectAtIndex: returns an object. valueForKey: returns an object. A CGFloat is not an object.
If you think this thing is an NSNumber object wrapping a number, then you can unwrap it, e.g. floatValue.
I don't very understand about the diference between (NSInteger)aNumberValue and [aNumberValue integerValue], then do some test. For example, here is a response data from server:
You can see it's an int but the value is hold by NSNumber. I retrieve the data by writting NSInteger count = (NSInteger) dic[#"count"];, and in Xcode debug area, saw this:
it's really a strange value but when I run po count and saw this:
anyway, the value is correct, but another strange thing is:
the number 2 is not less than 100!
Then I try NSInteger a = [dic[#"count"] integerValue] and saw the normal value in Xcode debug area:
and:
So, I am a little bit confused, what's the deference between (NSInteger)aNumberValue and [aNumberValue integerValue]?
NSNumber is a class; NSInteger is just a typedef of long, which is a primitive type.
dic[#"count"] is a pointer, which means that dic[#"count"] holds an address that points to the NSNumber instance. NSNumber has a method called integerValue which returns an NSInteger as the underlying value that the NSNumber instance represents. So you can conclude that [dic[#"count"] integerValue] gets you a long, and that's how you retrieve the value out of NSNumber.
You don't retrieve the value of NSNumber by casting it to NSInteger. That's because dic[#"count"], as I said, is a pointer. So by writing
NSInteger count = (NSInteger) dic[#"count"];
you are actually casting the pointer itself to an NSInteger, which has nothing to do with the actual represented value. The value 402008592 you see is just a decimal representation of the value of the pointer, which is an address.
The command po is used for printing objects, so lldb will actually try to print out the object at the address of count. That's why you get 2 back using po. You can try p count and you'll get 402008592.
About po count < 100: The expression (count < 100) is evaluated first; since count is really just an NSInteger of 402008592, it will evaluate to false.
The root issue is that Objective-C collection classes can only store Objective-C objects, not primitive types like float, int or NSInteger.
Therefore NSNumber provides a mechanism to store numbers and booleans in object form.
The value 402008592 looks like an address, so it's probably an NSNumber object containing an NSInteger value.
Don't get confused by the NS prefix of NSInteger and NSUInteger; they are still primitive types and not objects like NSNumber.
What is the difference between these two lines?
alertObj.AlertAddressed=[[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)] boolValue];
alertObj.AlertAddressed=(BOOL)[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)];
I'm getting a different result for these two lines - why?
Thanks in advance.
First one gives you actual bool value.
Second one type cast to BOOL the result of
[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)]
I don't know how good you are at pointers but I try to explain
First of all when you get an NSNumber it is an object, and the value of an object is at first it's pointer (so something like 0x0000af) this is simple an adress in the memory, and this address contains your NSNUmber wich contains the actual value (so let's say a bool information in your example)
It's pretty simple, when you do
(BOOL)alertObj.AlertAddressed=(BOOL)[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)];
what actually happen is the try to cast the 0x0000af part to a bool value... NOT what NSNumber contains (what you actually get depends on the current Pointer of the object when you try this)
alertObj.AlertAddressed=[[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)] boolValue];
this is something actually implemented in NSNumber and therefore it completly respects what the object does and gives you the bool saved in your NSNumber, and not a cast from it's pointer
NSNumber is an object, BOOL is a primitive type.
NSNumber is a class that wraps numbers, but you can't use to make operations, if you want you should unwrap calling a specific method. Since NSNumber is an object your variable is a pointer holding a reference to an object, not a value.
The first line is correct, the second is wrong because you are casting a pointer to a bool type.
alertObj.AlertAddressed=[[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)] boolValue]; This will convert you value to BOOL
alertObj.AlertAddressed=(BOOL)[NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)];This is like casting. Considers [NSNumber numberWithBool:sqlite3_column_int(compiledStatement, 9)] will return bool value.
I am new to objective C and trying to learn it. I am trying to write calculator program which performs simple mathematical calculation(addition, subtraction and so forth).
I want to create an array which stores for numbers(double value) and operands. Now, my pushOperand method takes ID as below:
-(void) pushOperand:(id)operand
{
[self.inputStack addObject:operand];
}
when I try to push double value as below:
- (IBAction)enterPressed:(UIButton *)sender
{
[self.brain pushOperand:[self.displayResult.text doubleValue]];
}
It gives my following error: "Sending 'double' to parameter of incompatible type 'id'"
I would appreciate if you guys can answer my following questions:
'id' is a generic type so I would assume it will work with any type without giving error above. Can you please help me understand the real reason behind the error?
How can I resolve this error?
id is a pointer to any class. Hence, it does not work with primitive types such as double or int which are neither pointers, nor objects. To store a primitive type in an NSArray, one must first wrap the primitive in an NSNumber object. This can be done in using alloc/init or with the new style object creation, as shown in the two snippets below.
old style
NSNumber *number = [[NSNumber alloc] initWithDouble:[self.displayResult.text doubleValue]];
[self.brain pushOperand:number];
new style
NSNumber *number = #( [self.displayResult.text doubleValue] );
[self.brain pushOperand:number];
I suggest using it with an NSNumber: Try not to abuse using id where you don't need to; lots of issues can arise if not.
- (void)pushOperand:(NSNumber *)operand
{
[self.inputStack addObject:operand];
}
- (IBAction)enterPressed:(UIButton *)sender
{
[self.brain pushOperand:#([self.displayResult.text doubleValue])];
}
I have a nsmutableArray "downloadProgress" which consists of a string and a floatvalue.
I need to find the float value from another class.
currently I am using
[[observedDownloads_ valueForKeyPath:#"#avg.downloadProgress"] floatValue];
but this wont give me the float value as it is inside the array downloadProgress.
How Do I access it.
you doing wrong. you can get Value like bellow example:-
[[observedDownloads_ valueForKeyPath:#"avg.downloadProgress"]objectAtIndex:1];