hey just a couple quick noob questions about writing my first ios app. Ive been searching through the questions here but they all seem to address questions more advanced than mine so im getting confused.
(1) All I want to do is turn a string into an array of integers representing the ASCII code. In other words, I want to convert:
"This is some string. It has spaces, punctuation, AND capitals."
into an array with 62 integers.
(2) How do I get back from the NSArray to a string?
(3) Also, are these expensive operations in terms of memory or computation time? It seems like it might be if we have to create a new variable at every iteration or something.
I know how to declare all the variables and im assuming I run a loop through the length of the string and at each iteration I somehow get the character and convert it into a number with some call to a built in command.
Thanks for any help you can offer or links to posts that might help!
NSString has a method to get the characters in an array:
ReplyDeleteNSString *string = "This is some string. It has spaces, punctuation, AND capitals.";
unichar *buffer = malloc(sizeof(unichar) * [string lenght]);
[string getCharacters:buffer range:NSMakeRange(0, [string length])];
If you check the definition of unichar, it's an unsigned short.
if you want to store the ascii values in an nsarray it is going to be expensive. NSArray can only hold objects so you're going to have to create an NSNumber for each ASCII value:
ReplyDeleteunsigned len = [string length];
NSMutableArray arr = [NSMutableArray arrayWithCapacity:len];
for (unsigned i = 0; i < len; ++i) {
[arr addObject:[NSNumber numberWithUnsignedShort:[string characterAtIndex:i]]];
}
2) to go back to an NSString you'll need to use an MSMutableString and append each byte to the NSMutableString.
After saying that I'd suggest you don't use this method if you can avoid it.
A better approach would be to use @EmilioPelaez's answer. To go back from a memory buffer to an NSString is simple and inexpensive compared to iterating and concatting strings.
NSString * stringFromMemory = [[NSString alloc] initWithBytes:buffer length:len encoding: NSASCIIStringEncoding];