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Objective-C const NSString * vs NSString * const
(2 answers)
Closed 8 years ago.
Can someone tell me the difference between the following 2 declarations of NSString?
NSString *const userName = #"ABC";
and
const NSString *userName = #"ABC";
The first is a constant pointer to an NSString object, while the second is a pointer to a constant NSString object.
First - A constant pointer (not modifiable) to an NSString (its value can be modified).
Second - A modifiable pointer to a constant NSString (its value can't be modified).
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Duplicate Symbol Error in Objective-C build?
(17 answers)
Closed 7 years ago.
the variable is inside Constants.h
ERROR is:
duplicate symbol _OSVShortTermFuelTrim1 in:
/Users/loximity/Library/Developer/Xcode/DerivedData/AutoCodesApp-hjoxbttreaujifdypikhbngdqihd/Build/Intermediates/AutoCodesApp.build/Debug-iphonesimulator/AutoCodesApp.build/Objects-normal/i386/ViewController.o
/Users/loximity/Library/Developer/Xcode/DerivedData/AutoCodesApp-hjoxbttreaujifdypikhbngdqihd/Build/Intermediates/AutoCodesApp.build/Debug-iphonesimulator/AutoCodesApp.build/Objects-normal/i386/FuelTrimViewController.o
and then I am using the above variables in two places, in view controller:
OSVShortTermFuelTrim1 = [NSString stringWithFormat:#"%# %#", [sensor valueStringForMeasurement1:NO], [sensor imperialUnitString]];
and in FuelTrimViewController"
fuelBank1.text = [NSString stringWithFormat:#"%#",OSVShortTermFuelTrim1];
You have to use extern to the declare the constants in the header file:
extern NSString *const YOUR_CONSTANT;
and then in an implementation file (.m), define the value:
NSString *const YOUR_CONSTANT = #"Hello World";
and, incidentally, your example code is the same, for all intents and purposes, to:
fuelBank1.text = OSVShortTermFuelTrim1;
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NSUInteger should not be used in format strings?
(4 answers)
Closed 8 years ago.
I'm trying to cast a NSUInteger to a string so I can print a message. From searching, it seems like I need to use stringWithFormat, but I am getting an error that an implicit cast not allowed with ARC.
Here's the line in question:
NSString *text = [[NSString stringWithFormat: (#"%li", NSUInteger)];
I've tried changing the format specifier to %lu with no help.
Thanks.
You probably have a variable of type NSUInteger, something like
NSUInteger myNumber;
Then you can convert it to a string like this:
NSString *text = [NSString stringWithFormat:#"%li", myNumber];
A solution that I prefer now is this:
NSString *text = [NSString stringWithFormat:#"%#", #(myNumber)];
This helps avoid compile warnings about incorrect number formatting codes (after a long time I still get confused in them).
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Closed 9 years ago.
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I've looked at several posts to answer my question but i keep getting errors.
I basically have an NSString that holds 2 characters...
myString = #"ABC";
All I want to do is assign the first character in myString to another NSString variable...
NSString *firstChar;
firstChar = [myString characterAtIndex:0];
I get this error when i do this:
Incompatible integer to pointer conversion assigning to 'unichar *' (aka 'unsigned short *') from 'unichar' (aka 'unsigned short')
What am I doing wrong?
NSString's characterAtIndex: returns a unichar, not a string, so you can't just assign it to another string. You need to create a string from it first:
NSString *myString = #"ABC";
unichar firstChar = [myString characterAtIndex:0];
NSString *string = [NSString stringWithCharacters:&firstChar length:1];
Of course, as DarkDust says, you can also use substringWithRange: to get a string from a subrange of a string:
[myString subStringWithRange:NSMakeRange(0, 1)]; // to get the first character
[myString subStringWithRange:NSMakeRange(1, 2)]; // to get the second and third characters
The characterAtIndex: method returns a unichar (an integer representation of the character). What you want is -[NSString substringWithRange:], like [myString substringWithRange:NSMakeRange(0, 1)];
This question already has answers here:
Get the extension of a file contained in an NSString
(6 answers)
Closed 9 years ago.
I want get extension (format file from NSString) but I dont know about it please tell me syntax for getting format file from NSString.
NSString *name = #"Xcode-tutorial.pdf"
I want get .pdf format and store in one variable
Use NSStrings pathExtension method:
NSString *fileExtension = [name pathExtension];
Did you look in the documentation? There is a method that does just that:
NSString *ext = [name pathExtension];
NSLog(#"%#", ext);
use this my dear:
NSString *a = [name pathExtension];
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
how to get substring of nsstring?
how do I get a substring in iOS?
I am new to iphone.In my project i have a string such as chapter1 but actually i want the substring 1 only how it is possible.if any body know this please help me
Check out the substringFromIndex: or substringToIndex: methods of NSString. You can find the documentation for NSString here.
Ex:
NSString *string = #"Chapter1";
NSString *newString = [string subStringFromIndex: ([string length] - 1)]; // => "1"