Programming on iOS
I will introduce how to set gradation on a background color of View and round corners of View on iOS.
Environment：Xcode 8, Swift 3
Use CAGradientLayer to set color gradation to UIView on iOS.
Set gradient colors to CAGradientLayer's colors method and set gradation direction using startPoint and endPoint of CAGradientLayer.
At last, set CAGradientLayer to UIView's layer using insertSublayer.
Use cornerRadius of UIView's CALayer for rounding corners of UIView.
I introduce how to capture screen and make a bitmap image on iOS this time.
Environment：Xcode 8.3, Swift 3
Sample code is below.
At first, use UIGraphicsBeginImageContextWithOptions, and make context of bitmap for capturing screen.
And write screen's objects' info at context.("self.view.layer.render(in:context)")
And use UIGraphicsGetImageFromCurrentImageContext, and get UIImage from context.
At last, use UIGraphicsEndImageContext, and close context.
You can do database programming by Core Data, O/R mapping tool for Sqlite, on iOS.
Environment: Xcode 8.3, Swift 3
At first, Check "Use Core Data" when project is created.
And code of Core Data Objects are created in AppDelegate.
Next, select "[project name].xcdatamodeld" and define table layout.
To save UIImage, select "Binary Data" in Type and check "Allow External Storage".
When the size of UIImage is big, URL of UIImage is saved in Core Data.
When you don't check "Allow External Storage", the time of saving core data will take and memory utilization will be increase instantly, and an application will crash.
After table layout definition, execute [Editor]-[Create NSManagedObject Subclass] on Xcode.
And class of table layout definition, NSManagedObject is created.
At last, declare "import Core Data" at the top of class using Core Data.
2.How to INSERT
At first, Make NSManagedObjectContext in AppDelegate.
Next, Make NSManagedObject from NSManagedObjectContext.
Let's see code for inserting new data by Core Data.
2.How to SELECT
Let's see code for selecting data by Core Data.
Use NSPredicate for designating searching options.
Use NSSortDescriptor and ascending option for designation sort options.
If you road UIImage, check UIImageOrientation.
If UIImageOrientation is down, you must invert UIImage.
3.How to UPDATE
Update value of data which is read.
Let's see code for updating data by Core Data.
4.How to DELETE
Delete data which is read.