Please forgive the simplicity of the question. I'm completely new to Objective C.
I'd like to know how to concatenate integer and string values and print them to the console.
This is what I'd like for my output:
10 + 20 = 30
In Java I'd write this code to produce the needed results:
System.Out.Println(intVarWith10 + " + " + intVarWith20 + " = " + result);
Objective-C is quite different. How can we concatenate the 3 integers along with the strings in between?
You can use following code
int iFirst,iSecond;
iFirst=10;
iSecond=20;
NSLog(#"%#",[NSString stringWithFormat:#"%d + %d =%d",iFirst,iSecond,(iFirst+iSecond)]);
Take a look at NSString - it has a method stringWithFormat that does what you require. For example:
NSString* yString = [NSString stringWithFormat:#"%d + %d = %d",
intVarWith10, intVarWith20 , result];
You can use C style syntax, with NSLog (If you just need to print)
NSLog(#"%d+%d=%d",intvarWith10,intvarWith20,result);
If you want a string variable holding the value
NSString *str = [NSString stringWithFormat:#"%d+%d=%d",intvarWith10,intvarWith20,result];
You have to create an NSString with format and specify the data type.
Something like this :
NSInteger firstOperand=10;
NSInteger secondOperand=20;
NSInteger result=firstOperand+secondOperand;
NSString *operationString=[NSString stringWithFormat:#"%d + %d = %d",firstOperand,secondOperand,result];
NSLog(#"%#",operationString);
NSString with format follows the C printf syntax
Check below code :
int i = 8;
NSString * tempStr = [NSString stringWithFormat#"Hello %d",i];
NSLog(#"%#",tempStr);
I strongly recommend you this link Objective-C Reference.
The Objective-C int data type can store a positive or negative whole number. The actual size or range of integer that can be handled by the int data type is machine and compiler implementation dependent.
So you can store like this.
int a,b;
a= 10;
b= 10;
then performing operation you need to first understand NSString.
C style character strings are composed of single byte characters and therefore limited in the range of characters that can be stored.
int C = a + b;
NSString *strAnswer = [NSString stringWithFormat:#"Answer %d + %d = %d", a , b, c];
NSLog(#"%#",strAnswer)
Hope this will help you.
Related
Hi I have made an IOS app that converts binary, hexadecimal and decimal values. It all works fine except for my decimal to binary conversion. Here is what I have. It returns 0s and 1s but far too many. Can anyone tell me why this is or help me with a better method?
NSString *newDec = [display text]; //takes user input from display
NSString *string = #"";
NSUInteger x = newDec;
int i = 0;
while (x > 0) {
string = [[NSString stringWithFormat:#"%u", x&1] stringByAppendingString:string];
x = x>> 1;
++i;
}
display.text = string; //Displays result in ios text box
Try this:
NSUInteger x = [newDec integerValue];
And next time don't ignore the Compiler's "Incompatible pointer to Integer conversion" hint...
Explanation: Afaik, assigning an object to an int, actually assigns the address of the object to that integer, not the content of the string (which is what you want).
The following is tried to print out N number of spaces (or 12 in the example):
NSLog(#"hello%#world", [NSString stringWithCharacters:" " length:12]);
const unichar arrayChars[] = {' '};
NSLog(#"hello%#world", [NSString stringWithCharacters:arrayChars length:12]);
const unichar oneChar = ' ';
NSLog(#"hello%#world", [NSString stringWithCharacters:&oneChar length:12]);
But they all print out weird things such as hello ÔÅÓñüÔÅ®Óñü®ÓüÅ®ÓñüÔ®ÓüÔÅ®world... I thought a "char array" is the same as a "string" and the same as a "pointer to a character"? The API spec says it is to be a "C array of Unicode characters" (by Unicode, is it UTF8? if it is, then it should be compatible with ASCII)... How to make it work and why those 3 ways won't work?
You can use %*s to specify the width.
NSLog(#"Hello%*sWorld", 12, "");
Reference:
A field width, or precision, or both, may be indicated by an asterisk
( '*' ). In this case an argument of type int supplies the field width
or precision. Applications shall ensure that arguments specifying
field width, or precision, or both appear in that order before the
argument, if any, to be converted.
This will get you what you want:
NSLog(#"hello%#world", [#"" stringByPaddingToLength:12 withString:#" " startingAtIndex:0]);
I think the issue you have is you are misinterpreting what +(NSString *)stringWithCharacters:length: is supposed to do. It's not supposed to repeat the characters, but instead copy them from the array into a string.
So in your case you only have a single ' ' in the array, meaning the other 11 characters will be taken from whatever follows arrayChars in memory.
If you want to print out a pattern of n spaces, the easiest way to do that would be to use -(NSString *)stringByPaddingToLength:withString:startingAtIndex:, i.e creating something like this.
NSString *formatString = #"Hello%#World";
NSString *paddingString = [[NSString string] stringByPaddingToLength: n withString: #" " startingAtIndex: 0];
NSLog(formatString, paddingString);
This is probably the fastest method:
NSString *spacesWithLength(int nSpaces)
{
char UTF8Arr[nSpaces + 1];
memset(UTF8Arr, ' ', nSpaces * sizeof(*UTF8Arr));
UTF8Arr[nSpaces] = '\0';
return [NSString stringWithUTF8String:UTF8Arr];
}
The reason your current code isn't working is because +stringWithCharacters: expects an array with a length of characters of 12, while your array is only 1 character in length {' '}. So, to fix, you must create a buffer for your array (in this case, we use a char array, not a unichar, because we can easily memset a char array, but not a unichar array).
The method I provided above is probably the fastest that is possible with a dynamic length. If you are willing to use GCC extensions, and you have a fixed size array of spaces you need, you can do this:
NSString *spacesWithLength7()
{
unichar characters[] = { [0 ... 7] = ' ' };
return [NSString stringWithCharacters:characters length:7];
}
Unfortunately, that extension doesn't work with variables, so it must be a constant.
Through the magic of GCC extensions and preprocessor macros, I give you.... THE REPEATENATOR! Simply pass in a string (or a char), and it will do the rest! Buy now, costs you only $19.95, operators are standing by! (Based on the idea suggested by #JeremyL)
// step 1: determine if char is a char or string, or NSString.
// step 2: repeat that char or string
// step 3: return that as a NSString
#define repeat(inp, cnt) __rep_func__(#encode(typeof(inp)), inp, cnt)
// arg list: (int siz, int / char *input, int n)
static inline NSString *__rep_func__(char *typ, ...)
{
const char *str = NULL;
int n;
{
va_list args;
va_start(args, typ);
if (typ[0] == 'i')
str = (const char []) { va_arg(args, int), '\0' };
else if (typ[0] == '#')
str = [va_arg(args, id) UTF8String];
else
str = va_arg(args, const char *);
n = va_arg(args, int);
va_end(args);
}
int len = strlen(str);
char outbuf[(len * n) + 1];
// now copy the content
for (int i = 0; i < n; i++) {
for (int j = 0; j < len; j++) {
outbuf[(i * len) + j] = str[j];
}
}
outbuf[(len * n)] = '\0';
return [NSString stringWithUTF8String:outbuf];
}
The stringWithCharaters:length: method makes an NSString (or an instance of a subclass of NSString) using the first length characters in the C array. It does not iterate over the given array of characters until it reaches the length.
The output you are seeing is the area of memory 12 Unicode characters long starting at the location of your passed 1 Unicode character array.
This should work.
NSLog(#"hello%#world", [NSString stringWithCharacters:" " length:12]);
I am a java programmer, I found that Java is very good at doing string.
If I want to do this objective c, how can I do in objective c ?
System.out.println("This is a " + 123 + " test");
To place an integer into a string, you can do this:
int n = 123;
NSString *s = [NSString stringWithFormat:#"This is a %d test", n];
There are numerous other ways. But concatenating strings with integers by + operator is not one of them. :)
To place an integer into a string, you can do this:
int number = 123;
NSString *string = [NSString stringWithFormat:#"This is a %i test", number];
Or if you want to NSLog you have to do this :
int number = 123;
NSLog(#"This is a %i test", number);
It is very EASY !!!
code below.
i'm tryind to obtain string answers like "a1", "c4"
this is what i'm having instead of "a1": "adresse finale: \340}00\214"
with this prinf:
printf("\nadresse finale: %s",[self convertCGPointToSquareAdress:self.frame.origin]);
the method is:
-(NSString *) convertCGPointToSquareAdress:(CGPoint ) point{
int x= point.x /PIECE_WIDTH;
int y=point.y/PIECE_WIDTH;
char lettreChiffre[2];
//char chiffre;
NSString *squareAdress;
//ascii a=97 , b=98... h=105
for (int i=97; i<105; i++) {
for (int j=8; j>0; j--) {
if(i-97==x && j-1==y ){
NSLog(#"enterrrrrrrrrred if convertCGPointToSquareAdress");
lettreChiffre[0]=i;
lettreChiffre[1]=(char) j;
printf(" lettreChiffre: %s ", lettreChiffre);
NSString *squareAdress=[NSString stringWithFormat:#"%s", lettreChiffre];
break;
}
}
}
return squareAdress;
}
can you please help me?
thanks in advance.
There are three problems I can see with your code:
1.
When you do
lettreChiffre[1]=(char) j;
remember j is a number between 1 and 8, so you're getting the ASCII character whose value is j, not the character 1...8. You should use
lettreChiffre[1]= '0' + j;
2.
lettreChiffre is a char array of length 2, which means there's no room for the terminal null character. This may work, but may give you gibberish. You should instead declare
char lettreChiffre[3];
lettreChiffre[2] = '\0';
3.
You're trying to use printf to print an NSString, which it can't do. Either use
NSLog(#"adresse finale: %#", mynsstring)
or convert the NSString back to a C-string:
printf("adresse finale: %s", [mynsstring UTF8String]);
Also, as noted by #dreamlax, you don't really need the loop. I assumed you were doing something else and ran into this trouble, so we're not really seeing the full code. But, if this is really the entirety of your code, then you can simply remove the loop as #dreamlax suggested.
What is the purpose of the loop? You have a loop that essentially brute forces a matrix to calculate the “square address”. Your method will also return an uninitialized pointer if x is greater than 8.
Your entire method could be made much simpler.
- (NSString *) convertCGPointToSquareAdress:(CGRect) point
{
unsigned int x = point.x / PIECE_WIDTH;
unsigned int y = point.y / PIECE_WIDTH;
// Do some range checking to ensure x and y are valid.
char lettreChiffre[3];
lettreChiffre[0] = 'a' + x;
lettreChiffre[1] = '1' + y;
lettreChiffre[2] = '\0';
return [NSString stringWithCString:letterChiffre encoding:NSASCIIStringEncoding];
}
I am trying to convert from an int to a string but I am having trouble. I followed the execution through the debugger and the string 'myT' gets the value of 'sum' but the 'if' statement does not work correctly if the 'sum' is 10,11,12. Should I not be using a primitive int type to store the number? Also, both methods I tried (see commented-out code) fail to follow the true path of the 'if' statement. Thanks!
int x = [my1 intValue];
int y = [my2 intValue];
int sum = x+y;
//myT = [NSString stringWithFormat:#"%d", sum];
myT = [[NSNumber numberWithInt:sum] stringValue];
if(myT==#"10" || myT==#"11" || myT==#"12")
action = #"numGreaterThanNine";
If you just need an int to a string as you suggest, I've found the easiest way is to do as below:
[NSString stringWithFormat:#"%d",numberYouAreTryingToConvert]
You can use literals, it's more compact.
NSString* myString = [#(17) stringValue];
(Boxes as a NSNumber and uses its stringValue method)
The commented out version is the more correct way to do this.
If you use the == operator on strings, you're comparing the strings' addresses (where they're allocated in memory) rather than the values of the strings. This is very occasional useful (it indicates you have the exact same string object), but 99% of the time you want to compare the values, which you do like so:
if([myT isEqualToString:#"10"] || [myT isEqualToString:#"11"] || [myT isEqualToString:#"12"])
== shouldn't be used to compare objects in your if. For NSString use isEqualToString: to compare them.
int val1 = [textBox1.text integerValue];
int val2 = [textBox2.text integerValue];
int resultValue = val1 * val2;
textBox3.text = [NSString stringWithFormat: #"%d", resultValue];
Simply convert int to NSString
use :
int x=10;
NSString *strX=[NSString stringWithFormat:#"%d",x];
Dot grammar maybe more swift!
#(intValueDemo).stringValue
for example
int intValueDemo = 1;
//or
NSInteger intValueDemo = 1;
//So you can use dot grammar
NSLog(#"%#",#(intValueDemo).stringValue);