Replacing instances of a character with two different characters in Objective-C - iphone

Question

I have a huge amount of NSStrings in a database that get passed to a view controller in an iOS app. They are formatted as "This is a message with $specially formatted$ content".
However, I need to change the '$' at the start of the special formatting with a '[' and the '$' at the end with ']'. I have a feeling I can use an NSScanner but so far all of my attempts have produced wackily concatenated strings!
Is there a simple way to recognise a substring encapsulated by '$' and swap them out with start/end characters? Please note that a lot of the NSStrings have multiple '$' substrings.
Thanks!

Answer 1

You can use regular expressions:
NSMutableString *str = [#"Hello $World$, foo $bar$." mutableCopy];
NSRegularExpression *regex;
regex = [NSRegularExpression regularExpressionWithPattern:#"\\$([^$]*)\\$"
options:0
error:NULL];
[regex replaceMatchesInString:str
options:0
range:NSMakeRange(0, [str length])
withTemplate:#"[$1]"];
NSLog(#"%#", str);
// Output:
// Hello [World], foo [bar].
The pattern #"\\$([^$]*)\\$" searches for
$<zero_or_more_characters_which_are_not_a_dollarsign>$
and all occurrences are then replaced by [...]. The pattern contains so many backslashes because the $ must be escaped in the regular expression pattern.
There is also stringByReplacingMatchesInString if you want to create a new string instead of modifying the original string.

Answer 2

I think replaceOccurrencesOfString: won't work cause you have start$ and end$.
But if you seperate the Strings with [string componentsSeperatedByString:#"$"] you get an Array of substrings, so every second string is your "$specially formatted$"-string

Answer 3

This should work!
NSString *str = #"This is a message with $specially formatted$ content";
NSString *original = #"$";
NSString *replacement1 = #"[";
NSString *replacement2 = #"]";
BOOL start = YES;
NSRange rOriginal = [str rangeOfString: original];
while (NSNotFound != rOriginal.location) {
str = [str stringByReplacingCharactersInRange: rOriginal withString:(start?replacement1:replacement2)];
start = !start;
rOriginal = [str rangeOfString: original];
}
NSLog(#"%#", str);
Enjoy Programming!

Answer 4

// string = #"This is a $special markup$ sentence."
NSArray *components = [string componentsSeparatedByString:#"$"];
// sanity checks
if (components.count < 2) return; // maybe no $ characters found
if (components.count % 2) return; // not an even number of $s
NSMutableString *out = [NSMutableString string];
for (int i=0; i< components.count; i++) {
[out appendString:components[i]];
[out appendString: (i % 2) ? #"]" : #"[" ];
}
// out = #"This is a [special markup] sentence."

Answer 5

Try this one
NSMutableString *string=[[NSMutableString alloc]initWithString:#"This is a message with $specially formatted$ content. This is a message with $specially formatted$ content"];
NSMutableString *string=[[NSMutableString alloc]initWithString:#"This is a message with $specially formatted$ content. This is a message with $specially formatted$ content"];
BOOL open=YES;
for (NSUInteger i=0; i<[string length];i++) {
if ([string characterAtIndex:i]=='$') {
if (open) {
[string replaceCharactersInRange:NSMakeRange(i, 1) withString:#"["];
open=!open;
}
else{
[string replaceCharactersInRange:NSMakeRange(i, 1) withString:#"]"];
open=!open;
}
}
}
NSLog(#"-->%#",string);
Output:
-->This is a message with [specially formatted] content. This is a message with [specially formatted] content