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!
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:
unsigned 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];
I ended up using the syntax I found here. Thanks for the help
How to convert ASCII value to a character in Objective-C?
NSString has a method to get the characters in an array:
NSString *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.
I have to read .csv file which has three columns. While parsing the .csv file, I get the string in this format Christopher Bass,\"Cry the Beloved Country Final Essay\",cbass#cgs.k12.va.us. I want to store the values of three columns in an Array, so I used componentSeparatedByString:#"," method! It is successfully returning me the array with three components:
Christopher Bass
Cry the Beloved Country Final Essay
cbass#cgs.k12.va.us
but when there is already a comma in the column value, like this
Christopher Bass,\"Cry, the Beloved Country Final Essay\",cbass#cgs.k12.va.us
it separates the string in four components because there is a ,(comma) after the Cry:
Christopher Bass
Cry
the Beloved Country Final Essay
cbass#cgs.k12.va.us
so, How can I handle this by using regular expression. I have "RegexKitLite" classes but which regular expression should I use. Please help!
Thanks-
Any regular expression would probably turn out with the same problem, what you need is to sanitize your entries or strings, either by escaping your commas or by highlighting strings this way: "My string". Otherwise you will have the same problem. Good luck.
For your example you would probably need to do something like:
\"Christopher Bass\",\"Cry\, the Beloved Country Final Essay\",\"cbass#cgs.k12.va.us\"
That way you could use a regexp or even the same method from the NSString class.
Not related at all, but the importance of sanitizing strings: http://xkcd.com/327/ hehehe.
How about this:
componentsSeparatedByRegex:#",\\\"|\\\","
This should split your string whereever " and , appear together in either order, resulting in a three-member array. This of course assumes that the second element in the string is always enclosed in parentheses, and the characters " and , never appear consecutively within the three components.
If either of these assumptions is incorrect, other methods to identify string components may be used, but it should be made clear that no generic solution exists. If the three component strings can contain " and , anywhere, not even a limited solution is possible in such cases:
Doe, John,\"\"Why Unescaped Strings Suck\", And Other Development Horror Stories\",Doe, John <john.doe#dev.null>
Hopefully there is nothing like the above in your CSV data. If there is, the data is basically unusable, and you should look into a better CSV exporter.
The regex you're searching for is: \\"(.*)\\"[ ^,]*|([^,]*),
in ObjC: (('\"' && string_1 && '\"' && 0-n spaces) || string_2 except comma) && comma
NSString *str = #"Christopher Bass,\"Cry, the Beloved Country ,Final Essay\",cbass#cgs.k12.va.us,som";
NSString *regEx = #"\\\"(.*)\\\"[ ^,]*|([^,]*),";
NSMutableArray *split = [[str componentsSeparatedByRegex:regEx] mutableCopy];
[split removeObject:#""]; // because it will print always both groups even if the other is empty
NSLog(#"%#", split);
// OUTPUT:
2012-02-07 17:42:18.778 tmpapp[92170:c03] (
"Christopher Bass",
"Cry, the Beloved Country ,Final Essay",
"cbass#cgs.k12.va.us",
som
)
RegexKitLite will add both strings to the array, therefore you will end up with empty objects for your array. removeObject:#"" will delete those but if you need to maintain true empty values (eg. your source has val,,ue) you have to modify the code to the following:
str = [str stringByReplacingOccurrencesOfRegex:regEx withString:#"$1$2∏"];
NSArray *split = [str componentsSeparatedByString:#"∏"];
$1 and $2 are those two strings mentioned above, ∏ is in this case a character which will most likely never appear in normal text (and is easy to remember: option-shift-p).
The last part looks like it will never contain a comma. Neither will the first one as far as I can see...
What about splitting the string like this:
NSArray *splitArr = [str componentsSeparatedByString:#","];
NSString *nameStr = [splitArr objectAtIndex:0];
NSString *emailStr = [splitArr lastObject];
NSString *contentStr = #"";
for(int i=1; i<[splitArr count]-1; ++i) {
contentStr = [contentStr stringByAppendingString:[splitArr objectAtIndex:i]];
}
This will use the first and last string as is, and combine the rest into the content.
Kind of a hack, but a name and an email address will never contain a comma, right?
Is the title guarantied to have the quotation marks? And is it the only component that can have them? Because then componentSeparatedByString:#"\"" should get you this:
Christopher Bass,
Cry, the Beloved Country Final Essay
,cbass#cgs.k12.va.us
Then use componentSeparatedByString:#"," or substringFrom/ToIndex: to get rid of the two commas in the first and last component.
Here's a solution using substring:
NSString* input = #"Christopher Bass,\"Cry, the Beloved Country Final Essay\",cbass#cgs.k12.va.us";
NSArray* split = [input componentsSeparatedByString:#"\""];
NSString* part1 = [split objectAtIndex:0];
NSString* part2 = [split objectAtIndex:1];
NSString* part3 = [split objectAtIndex:2];
part1 = [part1 substringToIndex:[part1 length] - 1];
part3 = [part3 substringFromIndex:1];
NSLog(part1);
NSLog(part2);
NSLog(part3);
hii every one
is there a way to get the character count in a string in obj c?
like how does the SMS app determine how big of a bubble the text view sends and receives? thanks a lot
You can use something like this:
NSString *str = #"Hello World!";
NSUInteger len = str.length;
If it is NSString then use str.length
If it is c string then use strlen(cString)
If it is a NSString then
[string length];
Not sure if you are talking about multi-bytes characters
length
Returns the number of Unicode
characters in the receiver.
- (NSUInteger)length
Return Value
The number of Unicode characters in
the receiver. Discussion
The number returned includes the
individual characters of composed
character sequences, so you cannot use
this method to determine if a string
will be visible when printed or how
long it will appear.
NSLog(#"Length of your string is %d",[yourString length]);
Say I have a string like "123alpha". I can use NSNumber to get the 123 out, but how can I determine the part of the string that NSNumber didn't use?
You can use NSScanner to both get the value and the rest of the string.
NSString *input = #"123alpha";
NSScanner *scanner = [NSScanner scannerWithString:input];
float number;
[scanner scanFloat:&number];
NSString *rest = [input substringFromIndex:[scanner scanLocation]];
If it is important to know exactly what is left after parsing the value this is a better approach than trying to trim characters. While I can't think of any particular bad input at the moment that would fail the solution suggested by the OP in the comment to this answer, it looks like a bug waiting to happen.
if your numbers are always at the beginning or end of a string and you want only the remaining characters, you could trim with a character set.
NSString *alpha = #"123alpha";
NSString *stripped = [alpha stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:#"0123456789"]];
If its starts out as a char * (as opposed to an NSString *), you can use strtol() to get the number and discover where the number ends in a single call.
I know it must be a very simple thing to do but I've never had to treat strings before (in Objective-C) and apparently there's not RegEx on Cocoa-Touch.
Well, the situation is:
I have a text field to get a value (money, such as 32.10 for instance).
The problem:
If the user types in a symbol such as #, /, # etc. my app will crash.
The Question: How can I treat this string to remove the symbols if there are any?
you can try this:
NSString *s = #"12.827##584";
NSCharacterSet *removeCharSet = [NSCharacterSet characterSetWithCharactersInString:#"/:##"];
s = [[s componentsSeparatedByCharactersInSet: removeCharSet] componentsJoinedByString: #""];
NSLog(#"%#", s);
You do get regex in Cocoa Touch.
Here's a good discussion of the varying degrees of regex power in iOS, the blocks example at the end should get you most of the way there.
http://volonbolon.net/post/861427732/text-handling-in-ios-4
I understand you're trying to figure out the number included in the UITextFields's text property and assign it to a float variable.
Try using an NSScanner for this:
NSScanner* textScanner = [NSScanner localizedScannerWithString:textfield.text];
float* floatValue;
[textScanner scanFloat:&floatValue];
floatValue now contains the parsed float value of your textfield.