multithreading - Thread-safe in delphi -

i have modify , change visual components in thread , know it's not safe doing this.

my question how write thread-safe code? possible? if can please give me simple example?

my code not threadsafe:

type   tmyworkerthread = class(tthread)       public          procedure execute; override;   end;  var   form1: tform1;  implementation  {$r *.dfm}  procedure tmyworkerthread.execute; begin   //codes   //working visual components end;  procedure tform1.button1click(sender: tobject); begin   tmyworkerthread.create(false); end; 

thank you.

writing thread safe code in delphi involves basic care have in other language, means deal race conditions. race condition happens when different threads access same data. way deal declare instance of tcriticalsection , wrap dangerous code in it.

the code below shows getter , setter of property that, hypotesis, has race condition.

constructor tmythread.create; begin   criticalx := tcriticalsection.create; end;  destructor tmythread.destroy; override; begin   freeandnil(criticalx); end;  function tmythread.getx: string; begin   criticalx.enter;   try     result := fx;       criticalx.leave;   end; end;  procedure tmythread.setx(const value: string); begin   criticalx.enter;   try     fx := value;       criticalx.leave;   end; end; 

notice use of single instance of tcriticalsection (criticalx) serialize access data member fx.

however, delphi have aditional consideration! vcl not thread safe, in order avoid vcl race conditions, operation results in screen changing must run in main thread. calling such code inside synchronize method. considering class above, should this:

procedure tmythread.showx; begin   synchronize(syncshowx); end;  procedure tmythread.syncshowx; begin   showmessage(inttostr(fx)); end; 

if have delphi 2010 or later, there easier way makes use of anonymous methods:

procedure tmythread.showx; begin   synchronize(procedure begin     showmessage(inttostr(fx));   end); end; 

i hope helps!