Accessing a specific string using rangeOfString in Objective C - objective-c

Question

I'm using NSURLConnection to pull data from a webpage. I'm looking to find a specific line of text to display in a basic app. I've converted my NSData to an NSString. The program successfully locates the string I'm looking for:
#"Most recent instantaneous value:
However, I need to actually pull and store the string that follows "instantaneous value: myString "
I'm noob, so I'm stuck. Here's my code:
- (void)viewWillAppear:(BOOL)animated
{
[super viewDidAppear:animated];
NSURLRequest *request = [NSURLRequest requestWithURL: [NSURL URLWithString:#"http://waterdata.usgs.gov/ga/nwis/uv?cb_72036=on&cb_00062=on&format=gif_default&period=1&site_no=02334400"] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
if (connection) {
// Connect
label.text = #"Connecting...";
myData = [[NSMutableData alloc] init];
} else {
// Error
}
}
- (void)connection:(NSURLConnection *) connection didReceiveData:(NSData *)data
{
[myData appendData:data];
}
-(void)connectionDidFinishLoading: (NSURLConnection *)connection {
response = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
label.text = response;
NSString *string1 = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
if ([string1 rangeOfString:#"Most recent instantaneous value: "].location == NSNotFound){
NSLog(#"Not found");
} else
{
NSLog(#"Found");
}
connection = nil;
}

Answer 1

You already have half the solution:
NSRange range = [string1 rangeOfString:#"Most recent instantaneous value: "];
if (range.location == NSNotFound) {
NSLog(#"Not found");
} else {
NSLog(#"Found");
// Method 1
NSString *string2 = [string1 stringByReplacingCharactersInRange:range withString:#""];
NSLog(#"%#", string2);
// Method 2
NSString *string3 = [string1 substringFromIndex:range.location+range.length];
NSLog(#"%#", string3);
}
Both methods produce the result you are looking for.

Answer 2

This depends no the format of what follows. You can easily use a regular expression to extract this value if it has a delimiter. For example, let's say it looks like this:
...Most recent instantaneous value: 74219MoredataBlahBLahBlah
This would be extracted using the regular expression "Most recent instantaneous value: ([0-9]+)"
However, if it is something like this
...Most recent instantaneous value: MyValueMoredataBlahBLahBlah
Then you are pretty much out of luck unless it is the same size each time
If it is like this
......Most recent instantaneous value: MyValue MoredataBlahBLahBlah
Then you can get it like this "...Most recent instantaneous value: ([A-Z,a-z]+ )" (note the space at the end inside the parenthesis).
Could you perhaps tell a bit more about the format of your value?
EDIT:
Since you know the length of your string, just do as shown above and when you get here:
NSString *restOfString = [string1 substringFromIndex:theRange.location+theRange.length];
Continue with this: NSString *cutString = [restOfString substringToIndex:8];

Answer 3

A good general tip for this sort of problem is to look at the documented methods in the NSString Class Reference. For example, the section under "Dividing Strings" has a few options for you, including
– substringFromIndex:
Your code might go something like this
NSString *string1 = [[NSString alloc] initWithData:myData encoding:NSUTF8StringEncoding];
NSRange theRange = [string1 rangeOfString:#"Most recent instantaneous value: "];
if (theRange.location == NSNotFound){
NSLog(#"Not found");
} else
{
NSString *restOfString = [string1 substringFromIndex:theRange.location+theRange.length];
}

Answer 4

ComponentSeparatedBy ":" should work.