文字列から指定した文字のみを取り出し生成するNSString拡張メソッド

2013-04-04 にQiitaに投稿した記事のアーカイブです。本文中のリンクは動作しないことがあります。

NSString *after = [before filteredString:hoge]の形で、before文字列からhoge指定文字のみを取り出し、NSStringを生成します。

#例

文字列	引数	結果
[phone]	0123456789	0353211111
AaBbCcDd	ABcd	ABcd
あのイーハトーヴォのすきとおった風	あいうえおかきくけこ	あきお
égalité	abcdefghijklmnop	gali

NSString+Filter.h

#import <Foundation/Foundation.h>

@interface NSString (Filter)
- (NSString *)filteredString:(NSString *)character;
@end

NSString+Filter.m

#import "NSString+Filter.h"

@implementation NSString (Filter)
- (NSString *)filteredString:(NSString *)character
{
    if ([self length] == 0)
        return [NSString string];
    
    NSCharacterSet* charSet;
    NSString* scanned;
    NSMutableString *exclude = [[NSMutableString alloc] init];
    NSMutableString *result = [[NSMutableString alloc] init];
    NSScanner* scanner;
    
    //Extract the character to exclude.
    charSet = [NSCharacterSet characterSetWithCharactersInString:character];
    scanner = [NSScanner scannerWithString:self];
    while(![scanner isAtEnd]) {
        if([scanner scanUpToCharactersFromSet:charSet intoString:&scanned]) {
            [exclude appendString:scanned];
        }
        [scanner scanCharactersFromSet:charSet intoString:nil];
    }
    
    //Filter unwanted characters from a string.
    charSet = [NSCharacterSet characterSetWithCharactersInString:exclude];
    scanner = [NSScanner scannerWithString:self];
    while(![scanner isAtEnd]) {
        if([scanner scanUpToCharactersFromSet:charSet intoString:&scanned]) {
            [result appendString:scanned];
        }
        [scanner scanCharactersFromSet:charSet intoString:nil];
    }
    
    return [NSString stringWithString:result];
}
@end

• NSMutableStringの filterString: はこちら

History

• 20130405 ver1.0.1 zero lengthに対応
• 20130404 ver1.0