GeneralTradingSarl
90 lines
5.5 KiB
Plaintext
90 lines
5.5 KiB
Plaintext
/****************************************************************/
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void OnStart() {ClassExample(); StructExample();}
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/***************************************************************
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Have you ever wondered how to safely return automatic objects
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from functions without memory leaks?
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Here is one option that will work in MQL.
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The technique is called 'copy constructor'. Make sure that
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all fields are copied, including complex data types,
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recursively.
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Please refer to the example code below, you will figure out
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how it works.
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*/
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void ClassExample()
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{
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Print(__FUNCTION__);
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A a1;
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A a2=Fa(); //object receive from function
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a1.Work();
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a1.Report(); //1 1 1 1
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a2.Report(); //3 3 3 3
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/*CONTINUE USE OBJECT FROM FUNCTION*/
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a2.Work();
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a2.Report(); //4 4 4 4
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return;
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}
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/***************************************************************
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PARTS OF CLASS A*/
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struct C {int mx; C():mx(0) {}};
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class D {public:int mx; D():mx(0) {} D(D &d):mx(d.mx) {}};
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/****************************************************************/
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class A
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{
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protected:
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int mx; //simple
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int ma[]; //array
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C mc; //struct
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D d; //class
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public:
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/*COPY CONSTRUCTOR*/
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A(A &a):mx(a.mx),d(a.d) {ArrayCopy(ma,a.ma); mc=a.mc;}
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/*EXPLICIT DEFAULT CONSTRUCTOR*/
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A():mx(0) {}
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/*METHODS*/
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void Work() {mx++; ArrayResize(ma,mx); mc.mx=mx; d.mx=mx;}
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void Report() {Print(mx," ",ArraySize(ma)," ",mc.mx," ",d.mx);}
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};
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/****************************************************************/
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A Fa()
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{
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A a;
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for(int i=0; i<3; i++)
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{a.Work();} //a lot of work
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return a; //object return
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}
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/***************************************************************
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Want to return a structure?
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Structures can be normally updated with function as parameters
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sent by reference.
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If you wish to RETURN a struct with function, it is also
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possible, but unlike classes, structs do not require an
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explicit 'copy constructor'.
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*/
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void StructExample()
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{
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Print(__FUNCTION__);
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B b1;
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B b2=Fb(); //struct receive from function
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b1.mx++;
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/**/
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Print(b1.mx," ",ArraySize(b1.ma)); // 1 0
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Print(b2.mx," ",ArraySize(b2.ma)); // 10 9
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return;
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}
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/****************************************************************/
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struct B
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{
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int mx;
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int ma[];
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B():mx(0) {} //constructor, not needed formally
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};
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/****************************************************************/
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B Fb()
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{
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B b;
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for(int i=0; i<10; i++)
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{b.mx++; ArrayResize(b.ma,i);} //work hard
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return b; //struct return
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}
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/**/
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