iOS Questions (Architecture & Design Patterns)

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Dispatch techniques: Dynamic dispatch and Static Dispatch

4 types of dispatch techniques — Inline  (Fastest) Static Dispatch Virtual Dispatch Dynamic Dispatch  (Slowest) Dynamic dispatch Swift  allows a class to override methods and properties declared in its superclasses. ... This technique, called  dynamic dispatch , increases language expressivity at the cost of a constant amount of runtime overhead for each indirect usage. Method Dispatch is the mechanism that helps to decide which operation should be executed, or more specifically, which method implementation should be used. Dynamic Dispatch  is supported only by  reference types ( i.e.  Class). The reason for this is that, for  dynamism , or  dynamic dispatch,  in short, we need  inheritance  and our  value types  do not support inheritance. To achieve  Dynamic Dispatch , we use inheritance, subclass a base class and then override an existing method of the base class. Also, we can make use of  dynamic  k...
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What’s the difference between var and let? Which one would you choose for properties in a struct and Class why?

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Let is an immutable variable, meaning that it cannot be changed, other languages call this a constant. Var is a mutable variable, meaning that it can be changed.   “Use let to make a constant and var to make a variable” let aPerson = Person (name: Foo , first: Bar ) //< data of aPerson are changeable, not the reference var aPerson = Person (name: Foo , first: Bar ) //< both reference and data are changeable. var aPersonA = Person (name: A , first: a) var aPersonB = Person (name: B , first: b) aPersonA = aPersonB //aPersonA now refers to Person (name: B , first: b) Value and Reference Type Reference Type(Class) Swift's  classes  are  mutable  a-priory var  +  class It can be  reassigned  or  changed let  +  class  =  constant of address It can  not  be  reassigned  and can be  changed Value(Struct, Enum) Swift's  struct  can change th...
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Certificate pinning and Alamofire

1.  Alamofire and URLSession.  both help you to make network requests in Swift.   Main advantage for Alamofire: Certificate pinning . It can take some time to sort this out and build this yourself. Asymmetric cryptography :  The second phase uses  public-key cryptography  or  asymmetric cryptography . This is a cryptographic system that uses pairs of keys: Public keys, which are widely disseminated and private keys, which only the owner knows. The third phase uses  symmetric-key cryptography , where you use the same key for both encryption of plaintext and decryption of ciphertext. In other words, you configure the app to reject all but one or a few predefined certificates or public keys. Whenever the app connects to a server, it compares the server certificate with the pinned certificate(s) or public key(s). If and only if they match, the app trusts the server and establishes the connection. You usually add a service’s certificate or public key a...
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