Slightly better than JumbledParamaterNetworkService.m . Here, you can move the payload creation (plus all the check it needs) to RPSUser class.

ModelParameterNetworkService.m

@class RPSUser

@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *email;
@property (nonatomic, copy) NSString *address;

/// Used only to create @p payloadDictionary.
@property (nonatomic, copy) NSString *password;

/// Payload dictionary made from this instance's properties.
- (NSDictionary *)payloadDictonary;

/// Rest of your implementation here...

@end


/// The result of this method will be sent via the @p RACSignal.
- (RACSignal *)registerNewUser:(RPSUser *)user
{
    NSDictionary *payload = [user payloadDictionary];
    
    // More logic or network call here...
    
    return networkRequestSignal;
}