I have static NSString as below:
static NSString *bowlerName;
In the code I am assigning it with some value as below:
-(void)setBowlerSpecifications:(int)playerId
{
Player *objPlayer = [CricketManagementDAL getBowlerSpecification :playerId];
[objPlayer retain];
bowlerSpecialSkill = objPlayer.specialSkill;
bowlerType = objPlayer.type;
bowlerName = objPlayer.playerName; // <------------
[objPlayer release];
}
Now, if I am referring to the same variable bowlerName in code anywhere else, I get the error: Variable is not a CFString.
Please help me.
It is an NSString but you are using it elsewhere in a context that expects a CFString, you can simply cast as follows
CFStringRef aCFString = (CFStringRef)aNSString;
Related
when i am using string concatenation in method(like -(IBAction)buttonDigitPressed:(id)sender) it shows the blank.I am recall the method automatically terminate the app. what is the problem plz replay me.
NSString *str= #"";
-(IBAction)buttonDigitPressed:(id)sender{
int a = (int)[sender tag];
str= [str stringByAppendingFormat:#"%i",a];
label1.text= str;
}
this is the code. check the code send me the replay where i am doing the mistake.
str in the method is an autoreleased object. Make it a copy property and do
self.str = [self.str stringByAppendingFormat:#"%i",a];
label1.text = self.str;
If str is same as label1.text then do this directly.
label1.text = [label1.text stringByAppendingFormat:#"%i",a];
If I have a pointer to an object foo with address (say) 0x809b5c0, I can turn that into an NSString by calling
NSString* fooString = [NSString stringWithFormat: #"%p", foo].
This will give me the NSString #"0x809b5c0".
What is the easiest way to reverse the process? That is, start with fooString, and get back my pointer to foo.
In its completeness...
To address-string
NSString *foo = #"foo";
NSString *address = [NSString stringWithFormat:#"%p", foo];
And back
NSString *fooAgain;
sscanf([address cStringUsingEncoding:NSUTF8StringEncoding], "%p", &fooAgain);
This snippet worked for me:
NSString *pointerString = #"0x809b5c0";
NSObject *object;
sscanf([pointerString cStringUsingEncoding:NSUTF8StringEncoding], "%p", &object);
Convert it to an integer, then cast it to whatever type it's supposed to be...
NSUInteger myInt = [ myStr integerValue ];
char * ptr = ( char * )myInt;
That said, I really don't understand why you will need this...
In my experience its easier to convert the pointer's address to an NSInteger, like this:
MyObject *object=[[MyObject alloc]init];
//...
NSInteger adress=(NSInteger)object;
Now reverse:
MyObject *otherObject=(MyObject*)adress;
Now: object==otherObject
Use an NSMapTable instead:
MyClass* p = [[MyClass alloc]init];
NSMapTable* map = [NSMapTable mapTableWithKeyOptions:NSMapTableStrongMemory valueOptions:NSMapTableStrongMemory];
[map setObject:whateverValue forKey:p];
// ...
for(MyClass* key in map) {
// ...
}
I'm new in objective-c, this is my first post. This is my problem:
In my main file I have a variable: NSString *var;
Then I have a function:
-(BOOL) myfunction:(NSString *)myvar {
myvar = #"OK!";
return YES;
}
Now in the main file I do:
NSString *var;
BOOL control = myfunction:var;
if(control)
NSLog(#"var is: %#",var);
but the output is "var is: ". If I built in debug mode, and put a breakpoint at the start of function myfunction the memory address of myvar is equal to var, but after the assignment the address of myvar is different from the address of var. How can I solve it? thanks in advance!
While the answers given so far are correct. I think a more pertinent question is why you would want to do this.
It looks you want to have a defensive programming style where the return code indicates success or failure.
A more Objective-C like way to do this would be to pass the string and an NSError ** as a parameter and return the string or a nil to indicate failure as described in the Error Handling Programming Guide
So the way to write this would be:
- (NSString *)aStringWithError:(NSError **)outError {
returnString = #"OK";
if (!returnString) {
if (outError != NULL) {
NSString *myErrorDomain = #"com.company.app.errors";
NSInteger errNo = 1;
*outError = [[[NSError alloc] initWithDomain:myErrorDomain code:errNo userInfo:nil] autorelease];
}
}
return returnString;
}
And to use it:
NSError *error;
NSString *stringVariable = [self aStringWithError:&error];
if (!stringVariable) {
// The function failed, so it returned nil and the error details are in the error variable
NSLog(#"Call failed with error: %ld", [error code]);
}
This is a trivial example, but you can see that you can construct and return far more meaningful information about the error rather than just whether it succeeded or not.
You can also use NSMutableString.
-(BOOL) myfunction:(NSMutableString *)myvar {
[myvar setString:#"OK!"];
return YES;
}
and change your call site as follows:
NSMutableString *var = [NSMutableString string];
BOOL control = [self myfunction:var];
if(control)
NSLog(#"var is: %#",var);
Syntactically you need to fix your myFunction invocation like so:
BOOL control = [self myfunction:var];
The real problem here is that inside of myFunction you are assigning a string value to a local string variable only, whereas you want to change the underlying string that it points to. This is usually the wrong approach in Obj-C, but you can do it like so:
-(BOOL)myfunction:(NSString **)myvar
{
*myvar = #"OK!";
return YES;
}
NSString *var;
BOOL control = [self myfunction:&var];
if(control)
NSLog(#"var is: %#",var);
I'm getting this warning "Format not a string literal and no format arguments? Any ideas?
-(BOOL)isFirstPointReached{
NSString *firstPoint = [NSString stringWithFormat:[pointsToFillArray objectAtIndex:0]];
NSString *lastPoint = [NSString stringWithFormat:[pointsToFillArray lastObject]];
if([firstPoint isEqualToString:lastPoint]){
return YES;
}
else{
return NO;
}
}
A few points...
The pointsToFillArray is an array of objects and the compiler does not know if it contains NSStrings or any other type of object. To get rid of the error you would cast it to (NSString*)
Secondly, the stringWithFormat is normally used to create a string from a few different pieces of data and does not need to be used in this case
Thirdly, you could just create pointers to the objects within the array and then do your check
The following should work for you:
NSString *firstPoint = (NSString*)[pointsToFillArray objectAtIndex:0];
NSString *lastPoint = (NSString*)[pointsToFillArray lastObject];
if ([firstPoint isEqualToString:lastPoint]) {
return YES;
}
I want to call a method which returns two values
basically lets say my method is like the below (want to return 2 values)
NSString* myfunc
{
NSString *myString = #"MYDATA";
NSString *myString2 = #"MYDATA2";
return myString;
return myString2;
}
So when i call it, i would use??
NSString* Value1 = [self myfunc:mystring];
NSString* Value2 = [self myfunc:mystring2];
I guess im doing something wrong with it, can anyone help me out?
Thanks
You can only return 1 value. That value can be a struct or an object or a simple type. If you return a struct or object it can contain multiple values.
The other way to return multiple values is with out parameters. Pass by reference or pointer in C.
Here is a code snippet showing how you could return a struct containing two NSStrings:
typedef struct {
NSString* str1;
NSString* str2;
} TwoStrings;
TwoStrings myfunc(void) {
TwoStrings result;
result.str1 = #"data";
result.str2 = #"more";
return result;
}
And call it like this:
TwoStrings twoStrs = myfunc();
NSLog(#"str1 = %#, str2 = %#", twoStrs.str1, twoStrs.str2);
You need to be careful with memory management when returning pointers even if they are wrapped inside a struct. In Objective-C the convention is that functions return autoreleased objects (unless the method name starts with create/new/alloc/copy).
You have a few options:
NSArray: Just return an array. Pretty simple.
Pointers: Pass in two pointers, and write to them instead of returning anything. Make sure to check for NULL!
Structure: Create a struct that has two fields, one for each thing you want to return, and return one of that struct.
Object: Same a structure, but create a full NSObject subclass.
NSDictionary: Similar to NSArray, but removes the need to use magic ordering of the values.
As you can only return one value/object, maybe wrap them up in an array:
-(NSArray*) arrayFromMyFunc
{
NSString *myString = #"MYDATA";
NSString *myString2 = #"MYDATA2";
return [NSArray arrayWithObjects:myString,myString2,nil];
}
You can then use it like this:
NSArray *arr = [self arrayFromMyFunc];
NSString *value1 = [arr objectAtIndex:0];
NSString *value2 = [arr objectAtIndex:1];
You could pass results back by reference, but this is easy to get wrong (syntactically, semantically, and from memory management point of view).
Edit One more thing: Make sure that you really need two return values. If they are quite independent, two separate function are often the better choice - better reusabilty and mentainable. Just in case you are making this as a matter of premature optimization. :-)
You can only directly return one value from a function. But there is a way of doing it.
-(void) myfuncWithVal1:(NSString**)val1 andVal2:(NSString**)val2
{
*val1 = #"MYDATA";
*val2 = #"MYDATA2";
}
Then to call it outside the method you'd use:
NSString* a;
NSString* b;
[self myfuncWithVal1:&a andVal2:&b];
void myfunc(NSString **string1, NSString **string2)
{
*string1 = #"MYDATA";
*string2 = #"MYDATA2";
}
...
NSString *value1, *value2;
myfunc(&value1, &value2);
Remember that you need to pass a pointer to a pointer when working with strings and other objects.
Wrap the two strings in an NSArray:
- (NSArray*)myFunc
{
NSString *myString = #"MYDATA";
NSString *myString2 = #"MYDATA2";
return [NSArray arrayWithObjects:myString, myString2, nil];
}
NSArray *theArray = [self myFunc]
NSString *value1 = [theArray objectAtIndex:0];
NSString *value2 = [theArray] objectAtIndex:1];
I see everyone has mentioned an NSArray but I'd go with an NSDictionary so the values don't have to be added in order or even at all. This means it is able to handle a situation where you only want to return the second string.
- (NSDictionary*)myFunction {
NSString *myString1 = #"string1";
NSString *myString2 = #"string2";
return [NSDictionary dictionaryWithObjectsAndKeys: myString1, #"key1", myString2, #"key2", nil];
}
NSDictionary *myDictionary = [self myFunction]
NSString *string1 = [myDictionary objectForKey:#"key1"];
NSString *string2 = [myDictionary objectForKey:#"key2"];