iOSのOS登録情報を使って認証なしでFacebook・Twitterでシェアする（LINEも追加） ref: http://qiita.com/kazuph/items/b1c98b4837dd1a161851

SampleViewController.m

#import "Social.h"
・・・
[Social facebookShare:self];
or
[Social twitterShare:self];
or
[Social lineShare:self];

Social.h

#import <Foundation/Foundation.h>

@interface Social : NSObject
+(void)facebookShare:(UIViewController *)vc;
+(void)twitterShare:(UIViewController *)vc;
+(void)lineShare:(UIViewController *)vc;
@end

Social.m

#import "Social.h"
#import <Social/Social.h>

@implementation Social

+(void)facebookShare:(UIViewController *)vc
{
    if ([SLComposeViewController isAvailableForServiceType:SLServiceTypeFacebook]) {
        SLComposeViewController *composeViewController = [SLComposeViewController composeViewControllerForServiceType:SLServiceTypeFacebook];
        void (^completion) (SLComposeViewControllerResult result) = ^(SLComposeViewControllerResult result) {
            [composeViewController dismissViewControllerAnimated:YES completion:nil];
        };
        [composeViewController setCompletionHandler:completion];
        [composeViewController setInitialText:@"テスト"];
        [composeViewController addURL:[NSURL URLWithString:@"http://google.com"]];
        [vc presentViewController:composeViewController animated:YES completion:Nil];
    }
}


+(void)twitterShare:(UIViewController *)vc
{
    if ([SLComposeViewController isAvailableForServiceType:SLServiceTypeTwitter]) {
        SLComposeViewController *composeViewController = [SLComposeViewController composeViewControllerForServiceType:SLServiceTypeTwitter];
        void (^completion) (SLComposeViewControllerResult result) = ^(SLComposeViewControllerResult result) {
            [composeViewController dismissViewControllerAnimated:YES completion:nil];
        };
        [composeViewController setCompletionHandler:completion];
        [composeViewController setInitialText:@"テスト"];
        [composeViewController addURL:[NSURL URLWithString:@"http://google.com"]];
        [vc presentViewController:composeViewController animated:YES completion:Nil];
    }
}

+(void)lineShare:(UIViewController *)vc {
    NSString *plainString = @"テスト";
    NSString *contentKey = (__bridge NSString *)CFURLCreateStringByAddingPercentEscapes(NULL, (CFStringRef)plainString, NULL, (CFStringRef)@"!*'();:@&=+$,/?%#[]", kCFStringEncodingUTF8 );
    NSString *contentType = @"text";
    NSString *urlString = [NSString stringWithFormat: @"http://line.naver.jp/R/msg/%@/?%@", contentType, contentKey];
    NSURL *url = [NSURL URLWithString:urlString];
    [[UIApplication sharedApplication] openURL:url];
}

@end