Prevent concurrent method execution and blocks - objective-c

Question

I'm writing a class to centralize remote calls to my backend.
The calls have to be authenticated with oauth, so in each methods, I first check if my token is valide, if not, I request a refreshed one.
Each method looks like this:
-(void)getRemoteDataAndRun:(nullable void(^)(NSDictionary * __nullable json))success
orFail:(nullable void(^)(AFHTTPRequestOperation * __nullable operation, NSError * __nullable error))failure {
[self checkOAuthTokenAndRun:^{
// my remote call
...
success(json);
} orFail:failure];
}
the method checkOAuthTokenAndRun check the token validity and request a new one if needed.
My problem is that I have to ensure that checkOAuthTokenAndRun is not called concurrently to prevent reads of credentials while it's refreshed (written).
I tried with NSLock but with blocks (multithreading), I get the following error:
*** -[NSLock lock]: deadlock (<NSLock: 0x7ffd9313d9b0> '(null)')
Here is the complete checkOAuthTokenAndRun method:
- (void)checkOAuthTokenAndRun:(void (^)())action orFail:(nullable void(^)(AFHTTPRequestOperation * __nullable operation, NSError * __nullable error))failure
{
NSLog(#"lock oauth check/refresh");
[oauthLock lock];
if (credential == nil || [credential isExpired])
{
NSLog(#"Credentials are null or expired");
if (credential == nil || credential.refreshToken == nil)
{
NSLog(#"Credentials are null or anonymous+expired");
[self getAnonymousCredentialsAndRun:^{
NSLog(#"unlock oauth");
[oauthLock unlock];
action();
} orFail:^(AFHTTPRequestOperation * _Nullable operation, NSError * _Nullable error) {
NSLog(#"unlock oauth");
[oauthLock unlock];
failure(operation, error);
}];
}
else
{
NSLog(#"Credentials are expired");
AFOAuth2Manager *OAuth2Manager = [[AFOAuth2Manager alloc] initWithBaseURL:[NSURL URLWithString:BaseURL] clientID:clientId secret:clientSecret];
[OAuth2Manager authenticateUsingOAuthWithURLString:#"/oauth/v2/token" refreshToken:credential.refreshToken success:^(AFOAuthCredential *_credential) {
credential = _credential;
NSLog(#"Received refreshed token");
[AFOAuthCredential storeCredential:credential
withIdentifier:OAuthProviderIdentifier];
NSLog(#"unlock oauth");
[oauthLock unlock];
action();
} failure:^(NSError *error) {
NSLog(#"Failed refreshing oauth token (%#)", [error localizedDescription]);
// remove refresh token
NSLog(#"Unable to get oauth token, delete credentials (%#)", [error localizedDescription]);
[AFOAuthCredential deleteCredentialWithIdentifier:OAuthProviderIdentifier];
credential = nil; //[AFOAuthCredential retrieveCredentialWithIdentifier:OAuthProviderIdentifier];
NSLog(#"unlock oauth");
[oauthLock unlock];
failure(nil, error);
}];
}
}
else { // run the action
NSLog(#"Credentials are valid (%#)", (credential.refreshToken.length ? #"refresh token defined" : #"refresh token not defined"));
NSLog(#"unlock oauth");
[oauthLock unlock];
action();
}
}
As you see, I'm using nested blocks, I don't know if this is the reason why I get the deadlocks.
Once again, I only want to prevent concurrent execution of checkOAuthTokenAndRun method
Thanks for your help

Answer 1

Network call are concurrent and they have to be concurrent. The problem with your code is you called a concurrent method inside another method which is itself concurrent. Solution to your problem:
Call method checkOAuthTokenAndRun first and if success(response from block) then call method getRemoteDataAndRun.
[self checkOAuthTokenAndRun:^{
if(success){
[self getRemoteDataAndRun:^{
}]
}
} orFail:failure];
//Above code snippet is just a example to solve your problem. You need redesign the blocks parameter