chain.m

// Wait for logout, then re-login
[[[loginController waitForLogoutCompletion] chain:^SPTask *(id value) {
    return [loginController waitForLoginCompletion];
}] addCallback:^(id value) {
    self.view.window.userInteractionEnabled = YES;
    [self.introDelegate introFlow:self finishedSuccessfully:YES didMerge:YES];
    self.introDelegate = nil;
}];


vs

SPTask *waitForRelog = [loginController waitForLogoutCompletion];
// Then wait for the login to happen.
waitForRelog = [waitForRelog chain:^SPTask *(id value) {
    return [loginController waitForLoginCompletion];
} on:dispatch_get_main_queue()];
// When that has happened we have switched user and can continue our flow..
[waitForRelog addCallback:^(id value) {
    self.view.window.userInteractionEnabled = YES;
    [self.introDelegate introFlow:self finishedSuccessfully:YES didMerge:YES];
    self.introDelegate = nil;
} on:dispatch_get_main_queue()];