Remove whitespace from string in Objective-C

问题:

I have a couple of strings. Some have a whitespace in the beginning and some not. I want to check if a string begins with a whitespace and if so remove it.

回答1:

There is method for that in NSString class. Check stringByTrimmingCharactersInSet:(NSCharacterSet *)set. You should use [NSCharacterSet whitespaceCharacterSet] as parameter:

NSString *foo = @" untrimmed string ";
NSString *trimmed = [foo stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

回答2:

You could use the stringByTrimmingCharactersInSet NSString method with the whitespaceAndNewlineCharacterSet NSCharacterSet as such:

NSString *testString = @"  Eek! There are leading and trailing spaces  ";
NSString *trimmedString = [testString stringByTrimmingCharactersInSet:
                             [NSCharacterSet whitespaceAndNewlineCharacterSet]];

回答3:

This will remove only the leading white space.

NSString *myString = @"   123   ";
NSLog(@"mystring %@, length %d",myString, myString.length);
NSRange range = [myString rangeOfString:@"^\\s*" options:NSRegularExpressionSearch];
myString = [myString stringByReplacingCharactersInRange:range withString:@""];
NSLog(@"mystring %@, length %d",myString, myString.length);

output

mystring    123   , length 9
mystring 123   , length 6

回答4:

I wrote a quick macro to reduce the amount of code needed to be written.

Step 1: Edit your app's PCH file, this should be named Project-Name-Prefix.pch

#define TRIM(string) [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]

Step 2: Enjoy writing way less code when you want to trim a string

NSLog(@"Output: %@ %@", TRIM(@"Hello        "), TRIM(@"World      "));

Output: Hello World