I'm trying to do some stuff with characterAtIndex and I'm stumped. if ([myString characterAtIndex:0]==0) works fine, if I'm looking for the number zero--but if I'm looking for a decimal point, if ([myString characterAtIndex:0]==.) just gives me an error. Is there another way to do this?
Check again. [myString characterAtIndex:0] == 0 will compile, but it won't do what you expect. That condition tests if the first character of your string is the character with the ASCII value of 0, which isn't the numeral 0: it's the NUL character.
-characterAtIndex: returns a value that you can compare with a character literal, which is a character enclosed in single quotes: '0' or '.', for example.
Perhaps something got lost in translation, but looking at your current question, I think this is what the solution would look like (compiles and executes as expected for me):
if([myString characterAtIndex:0] == '.') {
// ...
}
Note that you must use single-quotes (apostrophe), as these are c-style char items (technically ints) and not c-style strings (which would use double-quotes, and technically be an array/pointer)
characterAtIndex returns a unichar character, so use '.' instead.
ie: if ([myString characterAtIndex:0]=='.')
Related
I'm writing a program to make text that begins with /* and ends with */ a different color (syntax highlighting for a C comment). When I try this
#"/\*.*\*/";
I get unknown escape sequence. So I figured that to get a literal asterisk I had to use this
#"/[*].*[*]/";
and I get no errors, but when I use this code
commentPattern = #"/[*].*[*]/";
reg = [NSRegularExpression regularExpressionWithPattern:commentPattern options:kNilOptions error:nil];
results = [reg matchesInString:self.string options:kNilOptions range:NSMakeRange(0, [self.string length])];
for (NSTextCheckingResult *result in results)
{
[self setTextColor:[NSColor colorWithCalibratedRed:0.0 green:0.7 blue:0.0 alpha:1.0] range:result.range];
}
the text color of the comments doesn't change, but I don't see anything wrong with my regular expression. Can someone tell me why this wont work? I don't think it's a problem with the way I get the results or change their color, because I use the same method for other regular expressions.
You want to use this: "\\*".
\* is the escape sequence for * in regular expressions, but in C strings, \ also begins an escaped character token, so you have to escape that as well.
#"/\*.*\*/";
I get unknown escape sequence.
A string first converts escape sequences in the string, then the result is handed over to the regex engine. For instance, an escape sequence might be \t, which represents a tab, or \n which represents a newline. The string first converts an escape sequence to a special code. Your error is saying that \* is not a legal escape sequence for an NSString.
The regex engine needs to see a literal back slash followed by a *. To get a literal back slash in a string you need to write \\. However, for readability I prefer using a character class like you did with your second attempt.
You should NSLog what the results array contains to see what matches you are getting. If the matches are what you expect, then the problem is not with the regex.
I have an NSString instance (let's called it myString) containing the following UTF-8 unicode character: \xc2\x96 ( that is the long dash seen in, e.g., MS Word ).
When printing the NSString to the console using NSLog and the %# format specifier, the character is replaced by an upside-down question mark indicating that something is wrong - and when using it as text in a table cell, the unicode character simply appears as blank space ( not the empty string - a blank space ).
To solve this, I would like to replace the \xc2\x96 unicode character with a "normal" dash - at first I thought this should be a 10 sec. task but after some research I have not yet found the "right way" to do this and this is where I would like your help.
What I have tried:
When I print myString in hex like this NSLog(#"%x", myString) I get the hex value: 96 for the unicode character representing the unicode character \xc2\x96.
Using this information I have made the following implementation to replace it with its "normal" dash equivalent:
for(int index = 0; index < [myString length]; index++)
{
NSLog(#"Hex:'%x' Char:'%c'", [myString characterAtIndex:index],[myString characterAtIndex:index]);
if([[NSString stringWithFormat:#"%x", [myString characterAtIndex:index]] isEqualToString:#"96"])
myString = [myString stringByReplacingCharactersInRange:NSMakeRange(index, 1) withString:#"-"];
}
... it works, but my eyes don't like it, and I would like to know if this can be done in much more cleaner and "right" way? E.g. like C#'s String.Replace(char,char) which supports unicode characters .
So to wrap up:
I'm looking for the "right way" to replace unicode chars in a string - I have done some research, but apparently, there is only methods available that replaces occurrences of a given NSString with another NSString.
I have read the following:
https://stackoverflow.com/a/5223737/700926
https://stackoverflow.com/a/5217703/700926
https://stackoverflow.com/a/714009/700926
https://stackoverflow.com/a/668254/700926
https://stackoverflow.com/a/2039396/700926
... but all of them explains how to replace a given NSString with another NSString and do not cover how specific unicode characters ( in particular double byte ) can be replaced.
You can make your string mutable (i. e. use an NSMutableString instead of an NSString). Also, the call to [[NSString stringWithFormat:#"%x", character] isEqualToString:#"96"] is as inefficient as possible - why not simply if (character == 0x96)? All in all, try
NSString *longDash = #"\xc2\x96";
[string replaceOccurrencesOfString:longDash withString:#"-"];
Alright, I'm trying to write some code that removes words that contain an apostrophe from an NSString. To do this, I've decided to use regular expressions, and I wrote one, that I tested using this website: http://rubular.com/r/YTV90BcgoQ
Here, the expression is: \S*'+\S
As shown on the website, the words containing an apostrophe are matched. But for some reason, in the application I'm writing, using this code:
sourceString = [sourceString stringByReplacingOccurrencesOfRegex:#"\S*'+\S" withString:#""];
Doesn't return any positive result. By NSLogging the 'sourceString', I notice that words like 'Don't' and 'Doesn't' are still present in the output.
It doesn't seem like my expression is the problem, but maybe RegexKitLite doesn't accept certain types of expressions? If someone knows what's going on here, please enlighten me !
Literal NSStrings use \ as an escape character so that you can put things like newlines \n into them. Regexes also use backslashes as an escape character for character classes like \S. When your literal string gets run through the compiler, the backslashes are treated as escape characters, and don't make it to the regex pattern.
Therefore, you need to escape the backslashes themselves in your literal NSString, in order to end up with backslashes in the string that is used as the pattern: #"\\S*'+\\S".
You should have seen a compiler warning about "Unknown escape sequence" -- don't ignore those warnings!
if (myChar == '"')
if ([myChar compare:#"\""])
if ([myChar isEqual:#"\""])
if (myChar == #"\"")
None of the comparisons above seem to work. I need to check if myChar, which is taken from an NSString, is a quotation mark.
Any ideas?
The first one works, actually, if myChar is actually a char. The question is a bit unclear: are you trying to compare to a quote ('"') or a question mark ('?') ?
But yea, the first one works.
NSString *myString = [NSString stringWithFormat:#"%#",BernabÈu];
NSLog(#"%#", myString);
Above statement prints:
Bernab\u00c8u
Here 'BernabÈu' is Spanish character string.
Why is the "\u00c8u" appended? How to get rid of it?
The because the '\u00c8' is the unicode representation of the E. I don't have the code handy, but you will have to look into using Locale's I think to get it to print with the correct character. But don't worry. Java still understands that this is an E.
(don't have the correct 'E' handy either :-)