How to put an image in a Realm database?

问题:

I'm writing an iOS application using Swift 2 and I would like to save profile picture of an account locally in a Realm database. I can't find any documentation or people talking about that.

Is it possible? And how?

May be is it bad to do that?

回答1:

You can store images as NSData. Given you have the URL of an image, which you want to store locally, here is a code snippet how that can be achieved.

class MyImageBlob {
    var data: NSData?
}

// Working Example
let url = NSURL(string: "http://images.apple.com/v/home/cb/images/home_evergreen_hero_iphone_medium.jpg")!
if let imgData = NSData(contentsOfURL: url) {
    var myblob = MyImageBlob()
    myblob.data = imgData 

    let realm = try! Realm()
    try! realm.write {
        realm.add(myblob)
    }
}

May be it is a bad idea to do that?

The rule is simple: If the images are small in size, the number of images is small and they are rarely changed, you can stick with storing them in the database.

If there is a bunch images, you are better off writing them directly to the file system and just storing the path of the image in the database.

Here is how that can be done:

class MyImageStorage{
    var imagePath: NSString?
}

let url = NSURL(string: "http://images.apple.com/v/home/cb/images/home_evergreen_hero_iphone_medium.jpg")!
if let imgData = NSData(contentsOfURL: url) {
    // Storing image in documents folder (Swift 2.0+)
    let documentsPath = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0]
    let writePath = documentsPath?.stringByAppendingPathComponent("myimage.jpg")

    imgData.writeToFile(writePath, atomically: true)

    var mystorage = MyImageStorage()
    mystorage.imagePath = writePath

    let realm = try! Realm()
    try! realm.write {
         realm.add(mystorage)
    }
}

Please note: Both code samples are not reliable methods for downloading images since there are many pitfalls. In real world apps / in production, I'd suggest to use a library intended for this purpose like AFNetworking or AlamofireImage.

回答2:

ProblemSlover's solution updated for Swift 2.2:

Important Note: the only change is that now stringByAppendingPathComponent has been removed as of Swift 2.1, so you will get an error saying:

stringByAppendingPathComponent is unavailable: use URLByAppendingPathComponent on NSURL instead.

Please keep in mind that while it may be annoying, it has been removed for a reason and you should follow apple's recommendation to use NSURL instead. BUT if you wish to proceed with this solution, the fix for Swift 2.1+ is to explicitly cast documentsPath to NSString:

class MyImageStorage{
var imagePath: NSString?
}

let url = NSURL(string: "http://images.apple.com/v/home/cb/images/home_evergreen_hero_iphone_medium.jpg")!
if let imgData = NSData(contentsOfURL: url) {
    //Explicitly cast to NSString
    let documentsPath = (NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)[0] as NSString)
    let writePath = documentsPath.stringByAppendingPathComponent("myimage.jpg")

    imgData.writeToFile(writePath, atomically: true)

    var mystorage = MyImageStorage()
    mystorage.imagePath = writePath

    let realm = try! Realm()
    try! realm.write {
        realm.add(mystorage)
    }
}