取得webview的內容size

https://stackoverflow.com/questions/3936041/how-to-determine-the-content-size-of-a-uiwebview

- (void)webViewDidFinishLoad:(UIWebView *)aWebView {
    CGRect frame = aWebView.frame;
    frame.size.height = 1;
    aWebView.frame = frame;
    CGSize fittingSize = [aWebView sizeThatFits:CGSizeZero];
    frame.size = fittingSize;
    aWebView.frame = frame;

    NSLog(@"size: %f, %f", fittingSize.width, fittingSize.height);
}

要先設height到很小，再做[webView sizeToFit]; 或 [webView sizeThatFits:CGSizeZero];

正方形圖片

+ (UIImage *)resizeToSquareImageWithImage:(UIImage*)image toSize:(CGSize)newSize
{
    // crop image to square one
    CGSize oldSize = image.size;
    double newWidth = oldSize.width > oldSize.height ? oldSize.height : oldSize.width;
    CGRect newRect = CGRectMake(0.0, 0.0, newWidth, newWidth);

    CGImageRef sourceImageRef = [image CGImage];
    CGImageRef newImageRef = CGImageCreateWithImageInRect(sourceImageRef, newRect);
    UIImage *squareImage = [UIImage imageWithCGImage:newImageRef];
    CGImageRelease(newImageRef);
    // resize the image
    UIGraphicsBeginImageContext(newSize);
    [squareImage drawInRect:CGRectMake(0, 0, newSize.width, newSize.height)];
    UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
  
    return newImage;
}

從data查圖片格式

source: https://stackoverflow.com/questions/4147311/finding-image-type-from-nsdata-or-uiimage 

+ (NSString *)contentTypeForImageData:(NSData *)data {
    uint8_t c;
    [data getBytes:&c length:1];

    switch (c) {
    case 0xFF:
        return @"image/jpeg";
    case 0x89:
        return @"image/png";
    case 0x47:
        return @"image/gif";
    case 0x49:
    case 0x4D:
        return @"image/tiff";
    }
    return nil;
}

測試app遇到記憶體不足的情況

[[UIApplication sharedApplication] performSelector:@selector(_performMemoryWarning)];

在Debugger檢視圖片

檢視圖片//你可以在debugger直接看圖片

筆記一下rxswift遇到disposeBag的scope問題

//userRestoreObservable被訂閱時，會去server抓東西

//原本是在DataUpdate這個struct中寫disposeBag，setupInitialInfo完會釋放裡面的observable。

//但當userRestoreObservable的next closure做完，裡面的物件都被釋放掉，

於是setupInitialInfo的disposeBag也被釋放，就接不到server回傳時的callback。

//解決方法是把disposeBag改成外部注入，讓它被宣告在closure外部，這樣才可以保證裡面的closure不會先被釋放掉。

func fetchUserByRestoreInfo(restoreInfo: RestoreInfo, completion: (()->Void)?) {

        let disposeBag = DisposeBag()

        userRestoreObservable(restoreInfo).subscribeNext { (newUserObj) in

            prettyLog(newUserObj.debugDescription)

                var userDefault = self.userDefault

                userDefault.userPackage = newUserObj

                userDefault.isNewLounch = false

                DataUpdate().setupInitialInfo(disposeBag)

                completion?()

            }.addDisposableTo(disposeBag)

    }

present出二個modelView之後要dismiss回去rootViewController (iOS5.0之後適用)

if let presentingVC = self?.presentingViewController {

    self?.dismissViewControllerAnimated(false, completion: {

        presentingVC.dismissViewControllerAnimated(false, completion: nil)

    })

}

//這裡的重點是presentingVC是把當下VC給present出來的VC，你也可以看作parentViewController。

而你當前VC所present出來的VC，會叫presentedVC，也可以看作是childrenViewController.

presentingVC ---(present)---> yourViewController ---(present)---> presentedVC