Common ios operations

1. determine whether an element BOOLisValue = [keyArray containsObject: Q "aaa"] exists in the array. 2. Separate the strings by commas and save them to the array: NSArray * keyArray = [[NSArray alloc] init]; keyArray = [@ "winter melon, watermelon, pumpkin, bitter melon, silk melon" componentsSeparatedByString: @ ","]; 3. Extract the array and splice it into a string separated by commas: NSString * n = [keyArray componentsJoinedByString: @ ","]; 4. NSMutableArray is converted to NSArray * phoneA = [[NSArray alloc] init]; NSMutableArray * phoneArrayss = [[NSMutableArray alloc] init]; phoneA = [phon EArrayssmutableCopy]; 5. Obtain the local time (in case of HH in 24-hour format) NSDateFormatter * formatter = [[NSDateFormatter alloc] init]; [formattersetDateFormat: @ "yyyy-MM-dd HH: mm: ss"]; NSString * timeStr = [formatter stringFromDate: [NSDate date]; 6. Remove spaces in nsstring NSCharacterSet * whitespace = [NSCharacterSet whitespaceAndNewlineCharacterSet]; NSString * username = [mUsernameField stringValue]; username = [usernamestringByTrimmingChar ActersInSet: whitespace]; 7. Where to judge: IsNetworking * IsNetWork = [[IsNetworking alloc] init]; BOOL isNets = [IsNetWork isNetworkReachable]; if (isNets = NO) {// No network} else {// network} 8. append character: NSMutableString * string = [[NSMutableString alloc] init]; string = @ "hello"; [stringappendFormat: @ "China"]; 9. String replacement: replace all <in info with # NSString * stroneIntro = [info stringByReplacingOccurrencesOfString: @ "<" withString: @ "#"]; 10. String comparison: BoolIsTrue = [@ "Nob" isEqualToString: @ "Mob"] 11. a case-insensitive comparison String NSString * astring01 = @ "this is a String! "; NSString * astring02 = @" This is a String! "; BOOLresult = [astring01 caseInsensitiveCompare: astring02] = NSOrderedSame; 12. NSString * string1 = @" A String "; NSString * string2 = @" String "; NSLog (@ "string1: % @", [string1uppercaseString]); // upper case NSLog (@ "string2: % @", [string2lowercaseString]); // lowercase NSLog (@ "string2: % @", [string2capitalizedString]); // initial character size 13. Search for the substring NSString * string1 = @ "This is a string"; NSString * string2 = @ "string"; nsanger Ange = [string1 rangeOfString: string2]; intlocation = range. location; intleight = range. length; NSString * astring = [[NSString alloc] initWithString: [NSStringstringWithFormat: @ "Location: % I, Leight: % I", location, leight]; NSLog (@ "astring: % @", astring); [astringrelease]; 14. Extract the substring //-substringToIndex: extract the substring from the beginning of the string to the specified position, but does not include the NSString * string1 = @ "This is a string"; NSString * string2 = [string1 substr IngToIndex: 3]; NSLog (@ "string2: % @", string2); //-substringFromIndex: starts at the specified position (including characters at the specified position ), and all subsequent characters NSString * string1 = @ "This is a string"; NSString * string2 = [string1substringFromIndex: 3]; NSLog (@ "string2: % @", string2); //-substringWithRange: // truncate the substring NSString * string1 = @ "This is a string" randomly according to the given position and length "; NSString * string2 = [string1 substringWithRange: NSMakeRange (0, 4)]; NSLog (@ "string2: % @", string2 ); 15. Determine whether the string contains another string (prefix, suffix) // 01: Check whether the string starts with another string-(BOOL) hasPrefix: (NSString *) aString; NSString * String1 = @ "NSStringInformation.txt"; [String1hasPrefix: @ "NSString"] = 1? NSLog (@ "YES"): NSLog (@ "NO"); [String1hasSuffix: @ ". txt"] = 1? NSLog (@ "YES"): NSLog (@ "NO ");