How to convert PHAsset to UIImage in Objective-C

Question

I have an array filled with PHAsset objects (https://developer.apple.com/library/prerelease/ios/documentation/Photos/Reference/PHAsset_Class/index.html), and I want

Answer 1

image may be nil(seldom). It's better to evaluate, otherwise array add nil will crash app.

if(image){
    ima = image;
    [images addObject:ima];
}

Answer 2

Swift 3.0 Answer

let photoAsset = asset
        let manager = PHImageManager.default()
        var options: PHImageRequestOptions?
        options = PHImageRequestOptions()
        options?.resizeMode = .exact
        options?.isSynchronous = true
        manager.requestImage(
            for: photoAsset,
            targetSize: PHImageManagerMaximumSize,
            contentMode: .aspectFill,
            options: options
        ) { [weak self] result, _ in
            completion(result)
        }

options?.isSynchronous = true is very important

BOOL synchronous; // return only a single result, blocking until available (or failure). Defaults to NO

Answer 3

Swift 4.2

extension PHAsset {

    var image : UIImage {
        var thumbnail = UIImage()
        let imageManager = PHCachingImageManager()
        imageManager.requestImage(for: self, targetSize: CGSize(width: 100, height: 100), contentMode: .aspectFit, options: nil, resultHandler: { image, _ in
            thumbnail = image!
        })
        return thumbnail
    }
}                          

let image = asset.image 

Answer 4

For anyone struggling as much as I had on this issue, this is the way to go.

First set the requestOptions as:

self.requestOptions = [[PHImageRequestOptions alloc] init];
self.requestOptions.resizeMode   = PHImageRequestOptionsResizeModeExact;
self.requestOptions.deliveryMode = PHImageRequestOptionsDeliveryModeHighQualityFormat;

// this one is key
self.requestOptions.synchronous = YES;

and if there are multiple assets in an array filled with PHAsset objects, then add this code:

self.assets = [NSMutableArray arrayWithArray:assets];
PHImageManager *manager = [PHImageManager defaultManager];
NSMutableArray *images = [NSMutableArray arrayWithCapacity:[assets count]];

// assets contains PHAsset objects.
 __block UIImage *ima;

for (PHAsset *asset in self.assets) {
    // Do something with the asset

    [manager requestImageForAsset:asset
                       targetSize:PHImageManagerMaximumSize
                      contentMode:PHImageContentModeDefault
                          options:self.requestOptions
                    resultHandler:^void(UIImage *image, NSDictionary *info) {
                        ima = image;

                        [images addObject:ima];
                    }];


}

and now the images array contains all the images in uiimage format.