hello all hope someone can help with that. I was browsing the net and nothing really seems to make sense :S
so I have a string lets say:
"123" and I would like to use a function like:
padr("123", 5, 'x')
and the result should be:
"123xx"
Sorry but Objective-C is a nightmare when dealing with strings :S
You could create your own method to take the initial string, desired length, and padding character (as I was starting to do & also described in a few similar questions)
Or you could use the NSString method Apple already provides ;)
NSString *paddedString = [#"123"
stringByPaddingToLength: 5
withString: #"x" startingAtIndex:0];
See NSString Class Reference for this method.
What about the NSString method stringByPaddingToLength:withString:startingAtIndex:.
NSString* padr(NSString* string, NSUInteger length, NSString *repl)
{
return [string stringByPaddingToLength:length withString:repl startingAtIndex:0];
}
NSMutableString* padString(NSString *str, int padAmt, char padVal)
{
NSMutableString *lol = [NSMutableString stringWithString:str];
while (lol.length < padAmt) {
[lol appendFormat:#"%c", padVal];
}
return lol;
}
And the Call
int main(int argc, const char * argv[]) {
#autoreleasepool {
NSLog(#"%#", padString(#"123", 5, 'x'));
}
return 0;
}
Related
I wrote a method that works inside of an object, but now I want to extract it so that it's just a function. This is my broken command line tool program:
#import <Foundation/Foundation.h>
+ (NSMutableString *)reverseString:(NSString *)originalString {
NSMutableString *reversedString = [[NSMutableString alloc] init];
for (NSInteger i = originalString.length; i > 0; i--) {
[reversedString appendFormat:#"%c", [originalString characterAtIndex:i-1]];
}
return reversedString;
}
int main(int argc, const char * argv[]) {
#autoreleasepool {
NSString *originalString = #"original string";
NSMutableString *newString = [reverseString:originalString];
NSLog(#"Reversed string: %#", newString);
}
return 0;
}
My question is, how would I call the reverseString method from main()? I don't think I'm defining it properly. Do I have to declare it too? I know that the contents of my method work fine, but I don't know how to define it in a way that allows main to see it.
A "method" is, by definition, part of a class. There are two types, instance methods and class methods. To invoke an instance method, you need, well, an instance of the class. To invoke a class method, you don't need an instance. You can just invoke it directly on a class.
By contrast, there are also "functions". You don't need an instance or a class to invoke a function.
So, it sounds like you want a function. Functions are something that Objective-C inherits from C. The syntax for functions is different from the syntax for methods. Here's how your code might look using a function:
NSMutableString* reverseString(NSString *originalString) {
NSMutableString *reversedString = [[NSMutableString alloc] init];
for (NSInteger i = originalString.length; i > 0; i--) {
[reversedString appendFormat:#"%c", [originalString characterAtIndex:i-1]];
}
return reversedString;
}
int main(int argc, const char * argv[]) {
#autoreleasepool {
NSString *originalString = #"original string";
NSMutableString *newString = reverseString(originalString);
NSLog(#"Reversed string: %#", newString);
}
return 0;
}
By the way, your code does not "work fine". You can't iterate through a string by what it calls "characters" and treat all of them as independent. What NSString calls "characters" are actually UTF-16 code units. Not all Unicode characters can be expressed as single UTF-16 code units. Some need to use two code units in what's called a surrogate pair. If you split up and reverse a surrogate pair, you'll get an invalid string.
As a separate issue, Unicode has combining marks. For example, "é" can be expressed as U+0065 LATIN SMALL LETTER E followed by U+0301 COMBINING ACUTE ACCENT. Again, if you reorder those "characters", the accent will combine with a different character (or fail to combine at all).
The correct way to iterate through the composed character sequences of a string is to use the -[NSString enumerateSubstringsInRange:options:usingBlock:] method with the NSStringEnumerationByComposedCharacterSequences option.
By "I want to extract it so that it's just a function" you're implicitly saying "I want a C-style function, not an Objective-C class method". C-style functions are declared and called differently (blame history).
static NSMutableString * reverseString(NSString * originalString) {
...
}
...
NSMutableString *newString = reverseString(originalString);
I am trying to ask the user to enter their name and then return; "Hello and their name". I know its something simple that I am missing, but I just dont know what it is.
int main(int argc, const char * argv[]) {
#autoreleasepool {
NSString * name = #"";
NSLog(#"What is your name?");
scanf("%#", &name);
NSLog(#"Hello %#",name);
}
}
You're trying to mix Objective-C and C here. This is somewhat tricky to do, but let me see if I can help point you the right direction.
First, change:
NSString * name = #"";
scanf("%#", &name);
to:
char name[64];
scanf("%s", &name);
and see if that works better.
scanf is a C function that works with c types, and NSString is an objective C object which doesn't really work with "scanf".
(The "64" means that there's enough buffer space for 64 characters and if you blow past that, the app will likely crash).
Also, change:
NSLog(#"Hello %#",name);
to this:
NSLog(#"Hello %s",name);
As "%s" in the format tells NSLog that you're passing a C-style string and not a NSString object.
You're using an NSString object in C, which doesn't work. scanf expects a C string. Here's an example:
NSLog(#"What is your name?");
char name[40];
scanf("%s", name);
NSLog(#"Hello %#",[NSString stringWithCString:name encoding:NSUTF8StringEncoding]);
Or you can stay 100% in C:
printf("What is your name?");
char name[40];
scanf("%s", name);
printf("Hello %s", name);
I'm quite new to Cocoa programming and I'm tiring my best to create a program which will have the user input text into a text field and then press a button. When the button is pressed the text is supposed to replace certain substrings to certain characters. None of the substrings are longer than 2 characters, though some are a single character long. After the replacement has been performed the newly acquired text is to be put into another textfield.
Examples of substring replacements may be that "n" is supposed to be changed to "5", "nj" is supposed to be changed to "g" and "ng" is to be changed to "s". So the text "Inject the syringe now!" would be changed to "Igect the syrise 5ow!"
How can I achieve this in a simple and elegant way? I have tried the following code but it doesn't seem to work.
- (IBAction)convert:(id)sender {
NSMutableString *x;
[x setString:[self.input stringValue]];
NSMutableString *output1;
[output1 setString:#""];
NSMutableString *middle;
middle = [[NSMutableString alloc] init];
int s;
unsigned long length = [x length];
for (s = 0; s < length; s = s + 1) {
if (s + 2 <= length) { // if more than or equal to two characters left
[middle setString:[x substringWithRange:NSMakeRange(s, 2)]];
if ([middle isEqualToString:#"nj"]) {
[output1 appendToString:#"g"];
s = s+1;
} else if ([middle isEqualToString:#"ng"]) {
[output1 appendToString:#"s"];
s = s+1;
} else { // if no two-character sequence matched
[middle setString:[x substringWithRange:NSMakeRange(s, 1)]];
if ([middle isEqualToString:#"n"]) {
[output1 appendString:#"5"];
}
}
} else { // if less than two characters left
[middle setString:[x substringWithRange:NSMakeRange(s, 1)]];
if ([middle isEqualToString:#"n"]) {
[output1 appendString:#"5"];
}
}
}
[self.output setStringValue:output1];
}
Here, *x is where the text from input goes, *output1 is where the result is stored, *middle consists of the piece of text being tested, and input and output are the NSTextFields.
I guess you could achieve what you want with a quite a few different methods. Here is a simple one:
Define a map for values/replacements
Sort them by length (largest length first)
Match and replace
Something like this perhaps:
#import <Foundation/Foundation.h>
NSString * matchAndReplace(NSString *input, NSDictionary *map){
NSMutableString *_input = [input mutableCopy];
// Get all keys sorted by greatest length
NSArray *keys = [map.allKeys sortedArrayUsingComparator: ^(NSString *key1, NSString *key2) {
return [#(key2.length) compare:#(key1.length)];
}];
for (NSString *key in keys) {
[_input replaceOccurrencesOfString:key
withString:map[key]
options:NSLiteralSearch
range:NSMakeRange(0,_input.length)];
}
return [_input copy];
};
int main(int argc, char *argv[]) {
#autoreleasepool {
NSDictionary *mapping = #{
#"n": #"5",
#"nj": #"g",
#"ng": #"s"
};
NSString *input = #"Inject the syringe now!";
NSLog(#"Output: %#", matchAndReplace(input, mapping));
}
}
Which will produce:
Output: Igect the syrise 5ow!
Note: This is an over-simplified way to achieve what you want (obviously) and maybe requires a few adjustments to cover every edge case, but it's simpler than your version and I hope that will be helpful to you.
I just recently started learning Objective C, when i run the next program i get error
"program received signal: "EXC_BAD_ACCESS"
For the code line
if([*userChoice isEqualToString:#"yes"])
The full code is:
void initGame (void);
void restartGame(void);
void toGoOn(char *playerChoice);
int guess=-1;
int from=-1;
int to=-1;
bool playStatus=true;
bool gameStatus=true;
int answer=-1;
NSString *userChoice[10];
//if true the game is on
int main (int argc, const char * argv[])
{
#autoreleasepool {
GuessManager *game=GUESS;
NSLog(#"Hello, lets play");
NSLog(#"Please provide a positive range in which you would like to play");
do{
initGame();
[game setnumberToGuess:from :to];
do {
printf("Make you guess:");
scanf("%d", &guess);
[game setUserGuess:guess];
[game checkUserGuess];
if([game getDidIgetIt])
{
playStatus=false;
}
else
{
playStatus=true;
}
} while (playStatus);
restartGame();
}while(gameStatus);
printf("Thanks For Playing PanGogi Games! GoodBye");
}
return 0;
}
void initGame (void)
{
printf("from:");
scanf("%d",&from);
printf("to:");
scanf("%d",&to);
}
void restartGame(void)
{
printf("Would you like to continue?(yes/no)");
scanf("%s",&userChoice);
//scanf("%d",&answer);
// if(answer==1)
if([*userChoice isEqualToString:#"yes"])
{
gameStatus=true;
}
else
{
gameStatus=false;
}
}
I understand that its related to the NSString variable userChoice and how its used in
the if, but what i cant find is what am i doing wrong.
Please help :)
You have 3 errors in the code
1) I think you are getting confused with NSString and C style char array... You just need to use single NSString object to save multi character data..
NSString *userChoice;
2) Since you want to input data using scanf, you need a C style character array. scanf won't work with NSString types.
char tempArray[10];
int count = scanf("%s",&tempArray);
userChoice = [NSString stringWithBytes:tempArray length:count encoding: NSUTF8StringEncoding];
3) Now you can use NSString directly.. No need for pointer like syntax
if( [userChoice isEqualToString: #"yes"]){
.....
.....
}
You're using NSString as if it was char. It's not. It's a class that represents a string.
The scanf function is a C function and needs a char array, not an NSString.
char str[80];
scanf("%s", &str);
You can initialize an NSString object with a char array like this:
NSString *userChoice = [NSString stringWithCString:str encoding:NSASCIIEncoding];
And compare like this:
if ([userChoice isEqualToString:#"yes"]) {
...
} else {
...
}
Here's my code:
#import <Foundation/Foundation.h>
void PrintPathInfo() {
const char *path = [#"~" fileSystemRepresentation];
NSLog(#"My home folder is at '%#'", path);
}
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
PrintPathInfo();
[pool drain];
return 0;
}
And here's my problem:
Program received signal: “EXC_BAD_ACCESS”.
I really think the problem is my NSLog but I don't know how to solve it.
Could someone help me please? Thanks!
path is not an NSString, which is why that crashes. %# in a formatting string expects an object, and asks it for a description to get a string to print... because you are using a C style string, you need to use the standard C string formatters OR convert the const char * back to an NSString using the initWithCString:encoding: class method of NSString.
Staying with a const char *, you can use:
NSLog(#"My home folder is at '%s'", path);
which would work.
%# is for objects. (Like NSString). for const char* you will want the good old %s from the c's printf format codes.
See http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html
For the format specifies and their meanings