Come verificare se una NSString inizia con una certa altra stringa?

Question

Sto cercando di verificare se una stringa che sto per utilizzare come URL inizia con http. Il modo in cui sto cercando di verificare adesso sembra non funzionare. Ecco il mio codice:

NSMutableString *temp = [[NSMutableString alloc] initWithString:@"http://"]; 
if ([businessWebsite rangeOfString:@"http"].location == NSNotFound){ 
    NSString *temp2 = [[NSString alloc] init]; 
    temp2 = businessWebsite; 
    [temp appendString:temp2]; 
    businessWebsite = temp2; 
    NSLog(@"Updated BusinessWebsite is: %@", businessWebsite); 
} 

[web setBusinessWebsiteUrl:businessWebsite]; 

Qualche idea?

Answer 1

Prova questo: if ([myString hasPrefix:@"http"]).

A proposito, il test deve essere != NSNotFound anziché == NSNotFound. Ma dì che il tuo URL è ftp://my_http_host.com/thing, corrisponderà ma non dovrebbe.

Answer 2

mi piace usare questo metodo:

if ([[temp substringToIndex:4] isEqualToString:@"http"]) { 
    //starts with http 
} 

o ancora più semplice:

if ([temp hasPrefix:@"http"]) { 
    //do your stuff 
} 

Answer 3

Se stai controllando per "http:" probabilmente si vorrà ricerca case-insensitive:

NSRange prefixRange = 
    [temp rangeOfString:@"http" 
       options:(NSAnchoredSearch | NSCaseInsensitiveSearch)]; 
if (prefixRange.location == NSNotFound) 

Answer 4

Questa è la mia soluzione al problema. Rimuoverà le lettere che non sono necessarie e non fa distinzione tra maiuscole e minuscole.

- (NSArray *)sectionIndexTitlesForTableView:(UITableView *)tableView { 
    return [self generateSectionTitles]; 
} 

-(NSArray *)generateSectionTitles { 

    NSArray *alphaArray = [NSArray arrayWithObjects:@"A", @"B", @"C", @"D", @"E", @"F", @"G", @"H", @"I", @"J", @"K", @"L", @"M", @"N", @"O", @"P", @"Q", @"R", @"S", @"T", @"U", @"V", @"W", @"X", @"Y", @"Z", nil]; 

    NSMutableArray *sectionArray = [[NSMutableArray alloc] init]; 

    for (NSString *character in alphaArray) { 



     if ([self stringPrefix:character isInArray:self.depNameRows]) { 
      [sectionArray addObject:character]; 
     } 

    } 

    return sectionArray; 

} 

-(BOOL)stringPrefix:(NSString *)prefix isInArray:(NSArray *)array { 

    for (NSString *str in array) { 

     //I needed a case insensitive search so [str hasPrefix:prefix]; would not have worked for me. 
     NSRange prefixRange = [str rangeOfString:prefix options:(NSAnchoredSearch | NSCaseInsensitiveSearch)]; 
     if (prefixRange.location != NSNotFound) { 
      return TRUE; 
     } 

    } 

    return FALSE; 

} 

- (NSInteger)tableView:(UITableView *)tableView sectionForSectionIndexTitle:(NSString *)title atIndex:(NSInteger)index { 

    NSInteger newRow = [self indexForFirstChar:title inArray:self.depNameRows]; 
    NSIndexPath *newIndexPath = [NSIndexPath indexPathForRow:newRow inSection:0]; 
    [tableView scrollToRowAtIndexPath:newIndexPath atScrollPosition:UITableViewScrollPositionTop animated:NO]; 

    return index; 
} 

// Return the index for the location of the first item in an array that begins with a certain character 
- (NSInteger)indexForFirstChar:(NSString *)character inArray:(NSArray *)array 
{ 
    NSUInteger count = 0; 
    for (NSString *str in array) { 

     //I needed a case insensitive search so [str hasPrefix:prefix]; would not have worked for me. 
     NSRange prefixRange = [str rangeOfString:character options:(NSAnchoredSearch | NSCaseInsensitiveSearch)]; 
     if (prefixRange.location != NSNotFound) { 
      return count; 
     } 
     count++; 
    } 
    return 0; 
} 

Answer 5

versione Swift:

if line.hasPrefix("#") { 
    // checks to see if a string (line) begins with the character "#" 
}