I am trying to extract value of "points" element from JSON data using
NSString* encodedPoints = [apiResponse stringByMatching:#"points:\\\"([^\\\"]*)\\\"" capture:1L];
but there are more than one "points" elements in the JSON data. Plz help me i dont know much about regular expressions.
i am getting JSON Data from this link
You should use a JSON scanner.
Ensure that you have the JSON in an NSString, not an NSData.
Here is a method that uses an NSScanner instead of a regular expression:
NSMutableArray *pointList = [NSMutableArray array];
NSString *pointsString;
BOOL success = YES;
NSScanner *scanner = [NSScanner scannerWithString:encodedPoints];
while (YES) {
success = [scanner scanUpToString:#"points:\"" intoString:nil];
success = [scanner scanString:#"points:\"" intoString:nil];
if (success == NO)
break;
success = [scanner scanUpToString:#"\"" intoString:&pointsString];
[pointList addObject:pointsString];
}
// Show results by print lengths of the found points
for (NSString *point in pointList)
NSLog(#"point length: %i", point.length);
NSLog output:
point length: 22058
point length: 8889
You should use a JSON parser for this as that would be more correct/idea for dealing with JSON than using a regex which is prone to failure.
Related
I have the following NSMutableString:
#"1*2*3*4*5"
I want to find the first * and remove everything after it, so my string = #"1"; How do I do this?
NSMutableString *string = [NSMutableString stringWithString:#"1*2*3*4*5"];
NSRange range = [string rangeOfString:#"*"];
if (range.location != NSNotFound)
{
[string deleteCharactersInRange:NSMakeRange(range.location, [string length] - range.location)];
}
You could try to divide this string by a separator and get the first object
NSString *result = [[MyString componentsSeparatedByString:#"*"]objectAtIndex:0];
After calling componentsSeparatedByString:#"*" you'll get the array of strings, separated by *,and the first object is right what you need.
Here's yet another strategy, using the very flexible NSScanner.
NSString* beginning;
NSScanner* scanner = [NSScanner scannerWithString:#"1*2*3*4*5"];
[scanner scanUpToString:#"*" intoString:&beginning];
You could use -rangeOfString: to find the index of the first asterisk and use that with -substringToIndex: to extract a substring from the original input. Something like this perhaps...
NSMutableString *input = #"1*2*3*4*5";
// Finds the range of the first instance. See NSString docs for more options.
NSRange firstAsteriskRange = [input rangeOfString:#"*"];
NSString *trimmedString = [input substringToIndex:firstAsteriskRange.location + 1];
I am very new to iOS development. I am trying to parse a simple csv file that has about 10 lines separated by commas. I am using the code below but not able understand why NSScanner, when parsing the fields (fields in the code below) does not go to the next string after the comma. I have to execute the line
[fields scanCharactersFromSet:fieldCharSet intoString:nil];
to make it go past the delimiter. However, I don't have to do the same thing for lines - NSScanner automatically sets the position to the next line past the newline. In both cases I am using the same method - [lines scanUpToCharactersFromSet:intoString] Is there something I am not understanding?
Here is the test file I am trying to parse:
Name,Location,Number,Units
A,AA,4,mm
B,BB,3.5,km
C,CC,10.2,mi
D,DD,2,mm
E,EE,6,in
F,FF,2.8,m
G,GG,3.7,km
H,HH,4.3,mm
I,II,4,km
Here is my code:
-(void)parseFile {
NSCharacterSet *lineCharSet = [NSCharacterSet newlineCharacterSet];
NSCharacterSet *fieldCharSet = [NSCharacterSet characterSetWithCharactersInString:self.separator];
// import the file
NSStringEncoding *encoding = nil;
NSError *error = nil;
NSString *data = [[NSString alloc] initWithContentsOfURL:self.absoluteURL usedEncoding:encoding error:&error];
NSString *line,*field;
NSScanner *lines = [NSScanner scannerWithString:data];
while (![lines isAtEnd]) {
[lines scanUpToCharactersFromSet:lineCharSet intoString:&line];//automatically sets to next line - why?
NSLog(#"%#\n",line);
NSScanner *fields = [NSScanner scannerWithString:line];
while (![fields isAtEnd]) {
[fields scanUpToCharactersFromSet:fieldCharSet intoString:&field];
[fields scanCharactersFromSet:fieldCharSet intoString:nil]; //have to do this otherwise will not go to next symbol
NSLog(#"%#\n", field);
}
}
}
That's just the way NSScanner works. When you use scanUpToCharactersFromSet:intoString:, it scans characters up to but not including the characters in the set. If you want it to move past characters in the set, you have two options:
Make it scan those characters. You are doing this now using scanCharactersFromSet:intoString:. Another way you could do it is [fields scanString:self.separator intoString:nil].
Tell the scanner that the separator character is to be skipped, using setCharactersToBeSkipped:. However, this will make it hard for you to detect empty fields.
The scanner's default set of characters-to-be-skipped includes the newline. That's why your outer scanner skips the newline.
You could do this entirely using componentsSeparatedByString:, instead of using NSScanner. Example:
-(void)parseFile {
NSString *data = [[NSString alloc] initWithContentsOfURL:self.absoluteURL usedEncoding:encoding error:&error];
for (NSString *line in [data componentsSeparatedByString:#"\n"]) {
if (line.length == 0)
continue;
NSLog(#"line: %#", line);
for (NSString *field in [line componentsSeparatedByString:self.separator]) {
NSLog(#" field: %#", field);
}
}
}
How do I get string using NSScanner from a string which contains string as well as numbers too?
i.e. 001234852ACDSB
The result should be 001234852 and ACDSB
I am able to get numbers from the string using NSScanner and characters by using stringByReplacingOccurrencesOfString but I want to know, is that possible to get string from with the use of NSScanner or any other built in methods?
I would like to know the Regex for the same.
If you can guarantee that the string always consists of numbers followed by letters, then you could do the following with NSScanner:
NSScanner *scanner = [NSScanner scannerWithString:#"001234852ACDSB"];
NSString *theNumbers = nil;
[scanner scanCharactersFromSet:[NSCharacterSet decimalDigitCharacterSet]
intoString:&theNumbers];
NSString *theLetters = nil;
[scanner scanCharactersFromSet:[NSCharacterSet letterCharacterSet]
intoString:&theLetters];
A regular expression capturing the same things would look like this:
([0-9]+)([a-zA-Z]+)
Finally after google for the same and go through some information from net, I reached to my destination. With this I'm posting the code, this may help many who are facing the same problem as I have.
NSString *str = #"001234852ACDSB";
NSScanner *scanner = [NSScanner scannerWithString:str];
// set it to skip non-numeric characters
[scanner setCharactersToBeSkipped:[[NSCharacterSet decimalDigitCharacterSet] invertedSet]];
int i;
while ([scanner scanInt:&i])
{
NSLog(#"Found int: %d",i); //001234852
}
// reset the scanner to skip numeric characters
[scanner setScanLocation:0];
[scanner setCharactersToBeSkipped:[NSCharacterSet decimalDigitCharacterSet]];
NSString *resultString;
while ([scanner scanUpToCharactersFromSet:[NSCharacterSet decimalDigitCharacterSet] intoString:&resultString])
{
NSLog(#"Found string: %#",resultString); //ACDSB
}
You don't have to use a scanner to do it.
NSString *mixedString = #"01223abcdsadf";
NSString *numbers = [[mixedString componentsSeparatedByCharactersInSet:[[NSCharacterSet characterSetWithCharactersInString:#"0123456789"] invertedSet]] componentsJoinedByString:#""];
NSString *characters = [[mixedString componentsSeparatedByCharactersInSet:[[NSCharacterSet characterSetWithCharactersInString:#"abcdefghijklmnouprstuwvxyz"] invertedSet]] componentsJoinedByString:#""];
For other possible solution view this question Remove all but numbers from NSString
I have a large text file (about 10 MB). In the text file there are values like (without the empty lines between the rows, I couldn't format it here properly):
;string1;stringValue1;
;string2;stringValue2;
;string3;stringValue3;
;string4;stringValue4;
I'm parsing all the 'stringX' values to an Array and the 'stringValueX' to another string, using a pretty ugly solution:
words = [rawText componentsSeparatedByString:#";"];
NSEnumerator *word = [words objectEnumerator];
while(tmpWord = [word nextObject]) {
if ([tmpWord isEqualToString: #""] || [tmpWord isEqualToString: #"\r\n"] || [tmpWord isEqualToString: #"\n"]) {
// NSLog(#"%#*** NOTHING *** ",tmpWord);
}else { // here I add tmpWord the arrays...
I've tried to do this using NSScanner by following this example: http://www.macresearch.org/cocoa-scientists-part-xxvi-parsing-csv-data
But I received memory warnings and then it all crashed.
Shall I do this using NSScanner and if so, can anyone give me an example of how to do that?
Thanks!
In most cases NSScanner is better suited than componentsSeparatedByString:, especially if you are trying to preserve memory.
Your file could be parsed by a loop like this:
while (![scanner isAtEnd]) {
NSString *firstPart = #"";
NSString *secondPart = #"";
[scanner scanString: #";" intoString: NULL];
[scanner scanUpToString: #";" intoString: &firstPart];
[scanner scanString: #";" intoString: NULL];
[scanner scanUpToString: #";" intoString: &secondPart];
[scanner scanString: #";" intoString: NULL];
// TODO: add firstPart and secondPart to your arrays
}
You probably need to add error-checking code to this in case you get an invalid file.
You should use fast enumeration. It's far better than the one using objectEnumerator. Try this
for (NSString *word in words) {
// do the thing you need
}
I am grabbing a JSON array and storing it in an NSArray. However it includes JSON encoded UTF-8 strings, for example pass\u00e9 represents passé. I need a way of converting all of these different types of strings into the actual character. I have an entire NSArray to convert. Or I can convert it when it is being displayed, which ever is easiest.
I found this chart http://tntluoma.com/sidebars/codes/
Is there a convenient method for this or a library I can download?
thanks,
BTW, there is no way I can find to change the server so I can only fix it on my end...
You can use an approach based on the NSScanner. The following code (not bug-proof) can gives you a way on how it can work:
NSString *source = [NSString stringWithString:#"Le pass\\u00e9 compos\\u00e9 a \\u00e9t\\u00e9 d\\u00e9compos\\u00e9."];
NSLog(#"source=%#", source);
NSMutableString *result = [[NSMutableString alloc] init];
NSScanner *scanner = [NSScanner scannerWithString:source];
[scanner setCharactersToBeSkipped:nil];
while (![scanner isAtEnd]) {
NSString *chunk;
// Scan up to the Unicode marker
[scanner scanUpToString:#"\\u" intoString:&chunk];
// Append the chunk read
[result appendString:chunk];
// Skip the Unicode marker
if ([scanner scanString:#"\\u" intoString:nil]) {
// Read the Unicode value (assume they are hexa and four)
unsigned int value;
NSRange range = NSMakeRange([scanner scanLocation], 4);
NSString *code = [source substringWithRange:range];
[[NSScanner scannerWithString:code] scanHexInt:&value];
unichar c = (unichar) value;
// Append the character
[result appendFormat:#"%C", c];
// Move the scanner past the Unicode value
[scanner scanString:code intoString:nil];
}
}
NSLog(#"result=%#", result);
If you use the JSON Framework, then all you do is get your JSON string and convert it to an NSArray like so:
NSString * aJSONString = ...;
NSArray * array = [aJSONString JSONValue];
The library is well-written, and will automatically handle UTF8 encoding, so you don't need to do anything beyond this. I've used this library several times in apps that are on the store. I highly recommend using this approach.