How to check if NSString begins with a certain character - objective-c

Question

How do you check if an NSString begins with a certain character (the character *).
The * is an indicator for the type of the cell, so I need the contents of this NSString without the *, but need to know if the * exists.

Answer 1

You can use the -hasPrefix: method of NSString:
Objective-C:
NSString* output = nil;
if([string hasPrefix:#"*"]) {
output = [string substringFromIndex:1];
}
Swift:
var output:String?
if string.hasPrefix("*") {
output = string.substringFromIndex(string.startIndex.advancedBy(1))
}

Answer 2

You can use:
NSString *newString;
if ( [[myString characterAtIndex:0] isEqualToString:#"*"] ) {
newString = [myString substringFromIndex:1];
}

Answer 3

hasPrefix works especially well.
for example if you were looking for a http url in a NSString, you would use componentsSeparatedByString to create an NSArray and the iterate the array using hasPrefix to find the elements that begin with http.
NSArray *allStringsArray =
[myStringThatHasHttpUrls componentsSeparatedByString:#" "]
for (id myArrayElement in allStringsArray) {
NSString *theString = [myArrayElement description];
if ([theString hasPrefix:#"http"]) {
NSLog(#"The URL is %#", [myArrayElement description]);
}
}
hasPrefix returns a Boolean value that indicates whether a given string matches the beginning characters of the receiver.
- (BOOL)hasPrefix:(NSString *)aString,
parameter aString is a string that you are looking for
Return Value is YES if aString matches the beginning characters of the receiver, otherwise NO. Returns NO if aString is empty.

Answer 4

As a more general answer, try using the hasPrefix method. For example, the code below checks to see if a string begins with 10, which is the error code used to identify a certain problem.
NSString* myString = #"10:Username taken";
if([myString hasPrefix:#"10"]) {
//display more elegant error message
}

Answer 5

Use characterAtIndex:. If the first character is an asterisk, use substringFromIndex: to get the string sans '*'.

Answer 6

NSString *stringWithoutAsterisk(NSString *string) {
NSRange asterisk = [string rangeOfString:#"*"];
return asterisk.location == 0 ? [string substringFromIndex:1] : string;
}

Answer 7

Another approach to do it..
May it help someone...
if ([[temp substringToIndex:4] isEqualToString:#"http"]) {
//starts with http
}

Answer 8

This might help? :)
http://developer.apple.com/mac/library/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html#//apple_ref/occ/instm/NSString/characterAtIndex:
Just search for the character at index 0 and compare it against the value you're looking for!

Answer 9

This nice little bit of code I found by chance, and I have yet to see it suggested on Stack. It only works if the characters you want to remove or alter exist, which is convenient in many scenarios. If the character/s does not exist, it won't alter your NSString:
NSString = [yourString stringByReplacingOccurrencesOfString:#"YOUR CHARACTERS YOU WANT TO REMOVE" withString:#"CAN either be EMPTY or WITH TEXT REPLACEMENT"];
This is how I use it:
//declare what to look for
NSString * suffixTorRemove = #"</p>";
NSString * prefixToRemove = #"<p>";
NSString * randomCharacter = #"</strong>";
NSString * moreRandom = #"<strong>";
NSString * makeAndSign = #"&amp;";
//I AM INSERTING A VALUE FROM A DATABASE AND HAVE ASSIGNED IT TO returnStr
returnStr = [returnStr stringByReplacingOccurrencesOfString:suffixTorRemove withString:#""];
returnStr = [returnStr stringByReplacingOccurrencesOfString:prefixToRemove withString:#""];
returnStr = [returnStr stringByReplacingOccurrencesOfString:randomCharacter withString:#""];
returnStr = [returnStr stringByReplacingOccurrencesOfString:moreRandom withString:#""];
returnStr = [returnStr stringByReplacingOccurrencesOfString:makeAndSign withString:#"&"];
//check the output
NSLog(#"returnStr IS NOW: %#", returnStr);
This one line is super easy to perform three actions in one:
Checks your string for the character/s you do not want
Can replaces them with whatever you like
Does not affect surrounding code

Answer 10

NSString* expectedString = nil;
if([givenString hasPrefix:#"*"])
{
expectedString = [givenString substringFromIndex:1];
}