Does Swift has access modifiers? -


in objective-c instance data can public, protected or private. example:

@interface foo : nsobject {   @public     int x;   @protected:     int y;   @private:     int z;   } -(int) apple; -(int) pear; -(int) banana; @end

i haven't found mention of access modifiers in swift reference. possible limit visibility of data in swift?

as of swift 3.0.1, there 4 levels of access, described below highest (least restrictive) lowest (most restrictive).

1. open , public

enable entity used outside defining module (target). typically use open or public access when specifying public interface framework.

however, open access applies classes , class members, , differs public access follows:

  • public classes , class members can subclassed , overridden within defining module (target).
  • open classes , class members can subclassed , overridden both within , outside defining module (target).

// first.framework – a.swift  open class {} 

// first.framework – b.swift  public class b: {} // ok 

// second.framework – c.swift  import first  internal class c: {} // ok 

// second.framework – d.swift  import first  internal class d: b {} // error: b cannot subclassed

2. internal

enables entity used within defining module (target). typically use internal access when defining app’s or framework’s internal structure.

// first.framework – a.swift  internal struct {} 

// first.framework – b.swift  a() // ok 

// second.framework – c.swift  import first  a() // error: unavailable

3. fileprivate

restricts use of entity defining source file. typically use fileprivate access hide implementation details of specific piece of functionality when details used within entire file.

// first.framework – a.swift  internal struct {      fileprivate static let x: int  }  a.x // ok 

// first.framework – b.swift  a.x // error: x not available

4. private

restricts use of entity enclosing declaration. typically use private access hide implementation details of specific piece of functionality when details used within single declaration.

// first.framework – a.swift  internal struct {      private static let x: int      internal static func dosomethingwithx() {         x // ok     }  }  a.x // error: x unavailable

Comments

Post a Comment

Popular posts from this blog

inversion of control - Autofac named registration constructor injection -

does autofac support specifying registration name in components' constructors? example: ninject's namedattribute . you need use autofac.extras.attributed package on top achieve this so let's have 1 interface , 2 classes: public interface ihello { string sayhello(); } public class englishhello : ihello { public string sayhello() { return "hello"; } } public class frenchhello : ihello { public string sayhello() { return "bonjour"; } } then have consumer class, in want select instance injected: public class helloconsumer { private readonly ihello helloservice; public helloconsumer([withkey("en")] ihello helloservice) { if (helloservice == null) { throw new argumentnullexception("helloservice"); } this.helloservice = helloservice; } public string sayhello() { return this.helloservice.sayhello()...
Read more

ios - Change Storyboard View using Seague -

i have following code checks connection server, , depending on want change views if no connection found. nsstring *connect = [nsstring stringwithcontentsofurl:[nsurl urlwithstring:@"http://myserver.com"] encoding:nsutf8stringencoding error:nil]; if (connect == null) { [self performseguewithidentifier:@"network_failure" sender:self]; } else { // other code here } my problem not change views. have added storyboard segue between 2 views identifier of network_failure . not have navigation controller or that, problem? thanks help! no not problem. first of all, in objectivec exists nil object oriented null . must use that. so: if(connect == nil) or better: if(!connect) so due fact nil not same of null , probably code does't enter in if scope . you have been able discover breakpoint. anyway: be sure set trigger segue (line) 2 view controller , , name network_failure (that not best name. should instead view1toview2 ) as, m...
Read more

verilog - Systemverilog dynamic casting issues -

i've code snippet following in testbench function void write_to_port( my_data_type_base data ); my_data_type_extended data_ext; if(!$cast(data_ext, data)); `uvm_error(get_type_name(), "failed cast"); `uvm_info(get_name(), $psprintf("data_ext :\n%s", data_ext.sprint()), uvm_medium) // write data_ext out port.... endfunction when run it, i'm getting uvm_error "failed cast." i'm not quire sure why $cast not returning 1. can see, i'm printing out extended class data item after casting uvm_info. can see it's being cast properly. if don't use $cast if condition, don't runtime error. isn't coding practice use if dynamic cast check if $cast returning 1 ? what might reason behind cast not returning 1 in above case? i think semicolon on line 'if' not belong? i think consumes if statement, , uvm_error executes regardless of how if evaluates: if(!$cast(data_ext, data)); <- no semico...
Read more