Working with delegates synchronously - ios

Question

In the below code, self.theFiles prints the null. Because after calling [self.restClient loadMetadata:#"/"], getFiles method keeps working.
I want getFiles method to wait until [self.restClient loadMetadata:#"/"] finishes to get file list and put the data to self.theFiles object. But after [self.restClient loadMetadata:#"/"], getFiles keeps working.
#synthesize theFiles;
- (void)getFiles:(CDVInvokedUrlCommand*)command
{
if (![[DBSession sharedSession] isLinked]) {
[[DBSession sharedSession] linkFromController:self];
}
else
{
[self.restClient loadMetadata:#"/"];
}
NSLog(self.theFiles); //Prints null
NSLog(#"Finished");
}
#pragma mark DBRestClientDelegate methods
- (void)restClient:(DBRestClient*)client loadedMetadata:(DBMetadata*)metadata {
NSArray* validExtensions = [NSArray arrayWithObjects:#"txt", #"text", nil];
NSMutableArray* newPhotoPaths = [NSMutableArray new];
for (DBMetadata* child in metadata.contents) {
self.theFiles=child.path;
NSString* extension = [[child.path pathExtension] lowercaseString];
if (!child.isDirectory && [validExtensions indexOfObject:extension] != NSNotFound) {
[newPhotoPaths addObject:child.path];
}
}
NSLog(self.theFiles); //Prints the file list
}
Output:
null
Finished
/file1.txt
/file2.txt
..... the file list in my dropbox
Is it possible to work my getFiles method with delegate synchronously?
UPDATE
I updated my code. I want to lock the thread using NSLock but doesn't work. The same result.
#synthesize theFiles;
- (void)getFiles:(CDVInvokedUrlCommand*)command
{
if (![[DBSession sharedSession] isLinked]) {
[[DBSession sharedSession] linkFromController:self];
}
else
{
if ([self.theLock tryLock]) {
[self.restClient loadMetadata:#"/"];
NSLog(self.theFiles); //Prints null
NSLog(#"Finished");
}
}
}
#pragma mark DBRestClientDelegate methods
- (void)restClient:(DBRestClient*)client loadedMetadata:(DBMetadata*)metadata {
NSArray* validExtensions = [NSArray arrayWithObjects:#"txt", #"text", nil];
NSMutableArray* newPhotoPaths = [NSMutableArray new];
for (DBMetadata* child in metadata.contents) {
self.theFiles=child.path;
NSString* extension = [[child.path pathExtension] lowercaseString];
if (!child.isDirectory && [validExtensions indexOfObject:extension] != NSNotFound) {
[newPhotoPaths addObject:child.path];
}
}
NSLog(self.theFiles); //Prints the file list
[self.theLock unlock];
}