iOSアプリから、ツイッター・Facebookなど各種SNSやメール・メッセージなどで、画像付きのシェアをする方法です。

SLComposeViewControllerを使う場合はTwitter・Facebookなどの限られたSNSにしかポストできず、SNSを指定する方法も自前で実装する必要があります。

一方、UIActivityViewControllerを使うと、利用出来るSNS・ツールなどの選択画面が自動的に用意されます。

UIActivityViewControllerを使用した場合

いずれの方法もiOS6.0以降で、Social.frameworkが必要になります。

#import <Social/Social.h>

@interface SNSController : NSObject <UIActionSheetDelegate>

-(void) share:(UIViewController *)viewController : (NSString *)_txt : (NSString *)_hashTag : (NSString *)_url : (NSString *)_path;
@end

@implementation SNSController {
    UIViewController *viewController;
    NSString *txt, *hashTag;
    NSURL *url;
    UIImage *image;
}

-(void) share:(UIViewController *)_viewController : (NSString *)_txt : (NSString *)_hashTag : (NSString *)_url : (NSString *)_path {
    viewController = _viewController;
    txt = _txt;
    hashTag = _hashTag;
    url = [NSURL URLWithString:_url];
    if (_path) image = [UIImage imageWithContentsOfFile:_path];
    
    UIActionSheet *actionServiceType = [[UIActionSheet alloc] initWithTitle:@"Share result on ..." delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Twitter", @"Facebook", nil];
    [actionServiceType showInView:viewController.view];
}

#pragma mark - UIActionSheetDelegate
- (void)actionSheet:(UIActionSheet *)actionSheet didDismissWithButtonIndex:(NSInteger)buttonIndex {
    NSString *serviceType = nil;
    if (buttonIndex == 0) serviceType = SLServiceTypeTwitter;
    else if (buttonIndex == 1) serviceType = SLServiceTypeFacebook;
    
    if (serviceType) [self compose:serviceType];
}

- (void)compose:(NSString *)serviceType {
    NSString *str;
    if (serviceType == SLServiceTypeTwitter) str = [txt stringByAppendingFormat:@" %@", hashTag];
    else if (serviceType == SLServiceTypeFacebook) str = txt;
    else str = txt;

    SLComposeViewController *controller = [SLComposeViewController composeViewControllerForServiceType:serviceType];
    if (image) [controller addImage:image];
    [controller addURL:url];
    [controller setInitialText:str];
    [viewController presentViewController:controller animated:YES completion:nil];
}
@end

#import <Social/Social.h>

@interface SNSController : NSObject <UIActivityItemSource>

-(void) share:(UIViewController *)viewController : (NSString *)_txt : (NSString *)_hashTag : (NSString *)_url : (NSString *)_path;
@end

@implementation SNSController {
    NSString *txt, *hashTag;
}

-(void) share:(UIViewController *)viewController : (NSString *)_txt : (NSString *)_hashTag : (NSString *)_url : (NSString *)_path {
    txt = _txt;
    hashTag = _hashTag;
    NSURL *url = [NSURL URLWithString:_url];

    NSArray *array;
    float version = [[[UIDevice currentDevice] systemVersion] floatValue];
    if (version < 7.0) {
        array = [NSArray arrayWithObjects:self, url, nil];
    } else {
        txt = [txt stringByAppendingFormat:@" %@", url];
        array = [NSArray arrayWithObjects:self, nil];
    }

    if (_path) {
        UIImage *image = [UIImage imageWithContentsOfFile:_path];
        if (image) array = [NSArray arrayWithObjects:self, image, nil];
    }
    
    UIActivityViewController *avc = [[UIActivityViewController alloc] initWithActivityItems:array applicationActivities:nil];
    [viewController presentViewController:avc animated:YES completion:nil];
}

#pragma mark - UIActivityItemSource
-(id) activityViewController:(UIActivityViewController *)activityViewController itemForActivityType:(NSString *)activityType {
    if ([activityType isEqualToString:UIActivityTypePostToTwitter]) {
        return [NSString stringWithFormat:@"%@ %@", txt, hashTag];
    }
    return txt;
}

-(id) activityViewControllerPlaceholderItem:(UIActivityViewController *)activityViewController {
    return txt;
}
@end

iOS6.x台とiOS7.0以降で分岐させているのは、iOS7.0ではUIActivityViewControllerにNSURLを放り込むと、実行時にブラウザに飛んでしまうようになったためです。