isEqualToString not returning true

问题

The "Stopping" statement never gets printed even if you type 'stop' when running the program. Is the initWithUTF8String: method introducing extra formatting?

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    char holderText[256];

    fgets(holderText, 256, stdin);
    NSString *words = [[NSString alloc] initWithUTF8String:holderText];


    if ([words isEqualToString:@"stop"]) {

        NSLog(@"STOPPING");

    }
    NSLog(@"This is what you typed: %@", words);

    [pool drain];
    return 0;
}

回答1:

The code looks fine, even though you're leaking the words string. You need to add an [autorelease] on the end of that alloc call.

You could try initWithCString and also trim new lines and surrounding whitespace.

NSString *words = [[[NSString alloc] initWithCString:holderText] autorelease];
words = [words stringByTrimmingCharactersInSet:[NSCharacterSet newlineCharacterSet]];

回答2:

fgets will include the trailing newline in the string it gives you (except in the case where it wouldn't fit in the buffer but that's not so here), so it will be "stop\n" rather than "stop".

Changing the log line to:

NSLog(@"This is what you typed: [%@]", words);

should hopefully make it clear what's happening.

Either modify the comparison to take this into account, or trim the newline off before comparing.

回答3:

Since fgets will probably include a trailing newline, you might want to do a trim of all newlines in the string by using stringByTrimmingCharactersInSet::

NSString *trimmed = [words stringByTrimmingCharactersInSet:[NSCharacterSet newlineCharacterSet]];

if([trimmed isEqualToString:@"stop"]]) {
  //...
}

来源：https://stackoverflow.com/questions/6025663/isequaltostring-not-returning-true

标签

objective-c

cocoa

nsstring