MSMessage url stays nil after setting it to url of a file

Question

I have an app with an iOS 10 iMessage app. When I attach my file URL to an MSMessage message.URL is (null). I really don't know what's causing this. When I check the logs, I see a proper url: URL: file:///thisuser/... etc. However, message.URL logs (null).

I've build an Exporter class, this saves the file to disk and then returns the path for it.

+ (NSString *) saveToDisk:(NSDictionary *)dictionary {
    // Figure out destination name (in public docs dir)
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *zippedName = [self getExportFileName:dictionary withExtension:YES];
    NSString *zippedPath = [documentsDirectory stringByAppendingPathComponent:zippedName];

    // Export to data buffer
    NSData *gzData = [NSKeyedArchiver archivedDataWithRootObject:dictionary];

    if (gzData == nil) return FALSE;

    // Write to disk
    [gzData writeToFile:zippedPath atomically:YES];

    return zippedPath;
}

This will return something like: /Users/thisuses/Library/Developer/CoreSimulator/Devices/.../Documents/new-save.rst, where .rst is a custom file extension just for my app. This, in turn, is added to the MSMessage.

MSConversation *conversation = [self activeConversation];

MSMessageTemplateLayout *layout = [[MSMessageTemplateLayout alloc] init];
layout.image = [UIImage imageNamed:@"test"];
layout.caption = url.host;

MSMessage *message = [[MSMessage alloc] init];
message.layout = layout;

NSLog(@"Converter: %@", [Converter toDictionary:array]);
NSLog(@"Exporter: %@", [Exporter saveToDisk:[Converter toDictionary:array]]);
NSLog(@"URL: %@", [NSURL fileURLWithPath:[Exporter saveToDisk:[Converter toDictionary:array]]]);

message.URL = [NSURL fileURLWithPath:[Exporter saveToDisk:[Converter toDictionary:array]]];

NSLog(@"Message URL 1: %@", message.URL);

[conversation insertMessage:message completionHandler:^(NSError * error) {
    NSLog(@"MSConvo error: %@",error);
}];

== Edit: I added a check to the code to see if the Exporter returns a valid file path and turns out, it does.

NSURL *fileURL = [NSURL fileURLWithPath:[Exporter saveRequestToDisk:[Converter databaseToRequest:history]]];

if ([fileURL isFileURL]) {
    NSLog(@"is File URL!");
    message.URL = fileURL;
}

Answer 1

After looking into the docs and skimming this article, I think that the url property is not supposed to point to a file. Instead it should

[...][encode] data to be transmitted with the message.

I guess the right way to go is to

Encode your application’s data in the URL. For example, you can encode data as key-value pairs in the URL’s query string, as shown below:

guard let components = NSURLComponents(string: myBaseURL) else {
    fatalError("Invalid base url")
}

let size = NSURLQueryItem(name: "Size", value: "Large")
let count = NSURLQueryItem(name: "Topping_Count", value: "2")
let cheese = NSURLQueryItem(name: "Topping_0", value: "Cheese")
let pepperoni = NSURLQueryItem(name: "Topping_1", value: "Pepperoni")
components.queryItems = [size, count, cheese, pepperoni]

guard let url = components.url  else {
    fatalError("Invalid URL components.")
}

message.url = url

(Code taken from the docs, you might want to convert it to ObjC...)

So instead of converting your dictionary to NSData and writing it to a file, you might want to encode it into queryItems, possibly like this:

NSMutableArray *queryItems = [[NSMutableArray alloc] init]; // Or initWithCapacity for the sake of performance...
NSDictionary *dict = [Converter toDictionary:array];

for (id key in dict) {
    id value = queryDictionary[key];
    NSURLQueryItem *queryItem = [NSURLQueryItem queryItemWithName:key value:value];
    [queryItems addObject:queryItem];
}

[url setQueryItems:queryItems];