Objective-c – How to save video from assets url

alassetios4iphoneobjective cxcode

I want to save video to my app document from asset url. My asset url is as follows:-

"assets-library://asset/asset.MOV?id=1000000394&ext=MOV"

I tried this:-

NSString *str=@"assets-library://asset/asset.MOV?id=1000000394&ext=MOV";
NSData *videoData = [NSData dataWithContentsOfURL:[NSURL URLWithString:str]];
[videoData writeToFile:mypath atomically:YES];

but on the second line [NSData dataWithContentsOfURL:[NSURL URLWithString:str]] i got program crash with this reason:-
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSURL length]: unrecognized selector sent to instance

I want to know how to access asset video url.

Thanx for any help.

Best Answer

I think your best bet is to use the method

getBytes:fromOffset:length:error:

ALAssetRepresentation

You can get the default representation of an asset like so

ALAssetRepresentation *representation = [someVideoAsset defaultRepresentation];

So off the top of my head it should go something like this (I'm away from my Mac so this hasn't been tested)

ALAssetsLibrary *assetLibrary=[[ALAssetsLibrary alloc] init];
[assetLibrary assetForURL:videoUrl resultBlock:^(ALAsset *asset) {
    ALAssetRepresentation *rep = [asset defaultRepresentation];
    Byte *buffer = (Byte*)malloc(rep.size);
    NSUInteger buffered = [rep getBytes:buffer fromOffset:0.0 length:rep.size error:nil];
    NSData *data = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES];
    [data writeToFile:filePath atomically:YES];
} errorBlock:^(NSError *err) {
    NSLog(@"Error: %@",[err localizedDescription]);
}];

Where videoUrl is the asset url of the video you're trying to copy, and filePath is the path where you're trying to save it to.

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Objective-C: Calling selectors with multiple arguments

In Objective-C, a selector's signature consists of:

The name of the method (in this case it would be 'myTest') (required)
A ':' (colon) following the method name if the method has an input.
A name and ':' for every additional input.

Selectors have no knowledge of:

The input types
The method's return type.

Here's a class implementation where performMethodsViaSelectors method performs the other class methods by way of selectors:

@implementation ClassForSelectors
- (void) fooNoInputs {
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}
- (void) performMethodsViaSelectors {
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}
@end

The method you want to create a selector for has a single input, so you would create a selector for it like so:

SEL myTestSelector = @selector(myTest:);

Objective-c – How to disable ARC for a single file in a project

It is possible to disable ARC for individual files by adding the -fno-objc-arc compiler flag for those files.

You add compiler flags in Targets -> Build Phases -> Compile Sources. You have to double click on the right column of the row under Compiler Flags. You can also add it to multiple files by holding the cmd button to select the files and then pressing enter to bring up the flag edit box. (Note that editing multiple files will overwrite any flags that it may already have.)

I created a sample project that has an example: https://github.com/jaminguy/NoArc

xcode

See this answer for more info: Disable Automatic Reference Counting for Some Files

Best Answer

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Objective-c – How to disable ARC for a single file in a project

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