NSString_InstanceMethods

NSString

Inherits from: NSObject

Conforms to: NSObject, NSMutableCopying, NSSecureCoding, NSCopying

    stringByTrimmingCharactersInSet:

Returns a new string made by removing from both ends of the receiver characters contained in a given character set.

- (NSString *)stringByTrimmingCharactersInSet:(NSCharacterSet *)set

Parameters

set

A  character set containing the characters to remove from the receiver. set must not be nil.

Return Value

A new string made by removing from both ends of the receiver characters contained in set. if the receiver is composed entirely of characters from set, the empty string is returned.

Discussion

Use whitespaceCharacterSet or whitespaceAndNewlineCharacterSet to remove whitespace around strings.

    rangeOfString:

Finds and returns the range of the first occurrence of a given string within the receiver.

- (NSRange)rangeOfString:(NSString *)aString

Parameters

aString

The string to search for. This value must not be nil.

Raises an NSInvalidArgumentException if aString is nil.

Return Value

An NSRange structure giving the location and length in the receiver of  the first occurrence of aString. Returns {NSNotFound, 0} if aString is not found or is empty (@“”).

e.g.

NSRange *range = [“http://unpbook.com/small.git” rangeOfString:@“://”];

log:range.location = 4,length = 3

Discussion

Invokes rangeOfString:options: with no options.

    compare:options:

Compares the string with the specified string using the given options.

- (NSComparisonResult)compare:(NSString *)aString options:(NSStringCompareOptions)mask

Parameters

aString

The string with which to compare the receiver.

This value must not be nil. If this value is nil, the behavior is undefined and may change in future versions of OS X.

mask

Options for the search—you can combine any of the following using a C bitwise OR operator: NSCaseInsensitiveSearch, NSLiteralSearch, NSNumericSearch. See String Programming Guide for details on these options.

        NSCaseInsensitiveSearch 不区分大小写

NSLiteralSearch 区分大小写

NSNumericSearch 只比较字符串的个数，而不比较字符串的字面值

Return Value

The result of invoking compare:options:range: with a given mask as the options and the receiver’s full extent as the range.

Discussion

If you are comparing strings to present to the end-user, you should typically use localizedCompare: or localizedCaseInsensitiveCompare: instead, or use compare:options:range:locale: and pass the user’s locale.

e.g.

    NSString *scheme;

    if ([scheme compare:@"http"] options:NSCaseInsensitiveSearch] == NSOrderedSame) 

additional

    NSComparisonResult

    These constants are used to indicate how items in a request are ordered.

    enum {
   NSOrderedAscending = -1,
   NSOrderedSame,
   NSOrderedDescending
};
typedef NSInteger NSComparisonResult;