解析markdown中的图片地址

1、RegularParser.h

#import <Foundation/Foundation.h>

@interface RegularParser : NSObject

+ (NSArray *)imageUrlsInString:(NSString *)string trimedString:(NSString **)trimedString;

@end

2、RegularParser.m

#import "RegularParser.h"

static NSString *imageRegular = @"!\\[.*?\\]\()\\(.*?\\)";

@implementation RegularParser

+ (NSArray *)imageUrlsInString:(NSString *)string trimedString:(NSString **)trimedString {
    NSError *error;
    NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:imageRegular
                                                                           options:NSRegularExpressionCaseInsensitive
                                                                             error:&error];
    __block NSMutableArray *imagesArray = [NSMutableArray array];
    __block NSMutableString *mutableString = [string mutableCopy];
    __block NSInteger offset = 0;
    __block NSString *keyword = nil;
    __block NSString *imageUrl = nil;
    [regex enumerateMatchesInString:string
                            options:0
                              range:NSMakeRange(0, string.length)
                         usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
                             NSRange resultRange = [result range];
                             resultRange.location += offset;
                             // image
                             keyword = [regex replacementStringForResult:result
                                                                inString:mutableString
                                                                  offset:offset
                                                                template:@"$0"];
                             NSRange startRange = [keyword rangeOfString:@"]("];
                             if (startRange.length > 0) {
                                 NSRange range = NSMakeRange(startRange.location + startRange.length,
                                                             keyword.length - (startRange.location + startRange.length + 1));
                                 imageUrl = [keyword substringWithRange:range];
                                 [imagesArray addObject:imageUrl];
                             }
                             
                             [mutableString replaceCharactersInRange:resultRange withString:@""];
                             offset -= resultRange.length;
                             
                             *trimedString = mutableString;
                         }];
    return imagesArray;
}

@end

3、示例

NSString *markdownString = @"![](http://dl2.iteye.com/upload/attachment/0105/4183/f2b93502-e02b-3259-9837-d3dd14151e9d.png) When I say Japanese-Chinese food I'm not referring to some new type of restaurant serving both Japanese and Chinese food. This means the restaurant serves Chinese food prepared for Japanese tastes. ![](http://dl2.iteye.com/upload/attachment/0103/6545/d0590cfe-bd18-3c25-8b1b-2190c0526b5c.png) This is **subuta** -- sweet and sour pork, this one photo showing the meal set (tenshoku in Japanese). It's one of many Chinese dishes this restaurant serves... and they have **A LOT**!";
NSLog(@"%@", [RegularParser imageUrlsInString:markdownString trimedString:&markdownString]);