NSString写入文件，append模式实现

Link：<a target=_blank href="http://iphonedevelopment.blogspot.com/2010/08/nsstring-appendtofileusingencoding.html">http://iphonedevelopment.blogspot.com/2010/08/nsstring-appendtofileusingencoding.html</a>
    <pre name="code" class="objc">#import <Foundation/Foundation.h>

@interface NSString(MCFileAppend)
- (BOOL)appendToFile:(NSString *)path usingEncoding:(NSStringEncoding)encoding;
@end

@implementation NSString(MCFileAppend)
- (BOOL)appendToFile:(NSString *)path usingEncoding:(NSStringEncoding)encoding
{
    NSFileHandle *fh = [NSFileHandle fileHandleForWritingAtPath:path]; 
    if (fh == nil)
        return [self writeToFile:path atomically:YES encoding:encoding error:nil];
    
    [fh truncateFileAtOffset:[fh seekToEndOfFile]];
    NSData *encoded = [self dataUsingEncoding:encoding];
    
    if (encoded == nil) return NO;
    
    [fh writeData:encoded];

<pre name="code" class="objc">    [fh closeFile];

return YES;}@end