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77 lines
No EOL
1.8 KiB
C++
77 lines
No EOL
1.8 KiB
C++
#include "Tutorial.h"
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void ValueTutorial()
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{
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/// .Value
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/// Value is sort of equivalent of polymorphic data types from scripting languages like Python
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/// or JavaSript. `Value` can represent values of concrete types, some types also have
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/// extended interoperability with `Value` and it is then possible to e.g. compare `Value`s
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/// containing such types against each other or serialize them for persistent storage.
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/// Usually, Value compatible types define typecast operator to `Value` and constructor
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/// from `Value`, so that interaction is for the most part seamless:
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Value a = 1;
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Value b = 2.34;
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Value c = GetSysDate();
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Value d = "hello";
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DUMP(a);
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DUMP(b);
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DUMP(c);
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DUMP(d);
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int x = a;
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double y = b;
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Date z = c;
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String s = d;
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DUMP(x);
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DUMP(y);
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DUMP(z);
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DUMP(s);
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/// As for primitive types, Value seamlessly works with `int`, `int64`, `bool` and `double`.
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/// Casting `Value` to a type that it does not contain throws an exception:
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try {
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s = a;
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DUMP(s); // we never get here....
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}
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catch(ValueTypeError) {
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LOG("Failed Value conversion");
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}
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/// However, conversion between related types is possible (as long as it is supported by
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/// these types):
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double i = a;
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int j = b;
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Time k = c;
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WString t = d;
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DUMP(i);
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DUMP(j);
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DUMP(k);
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DUMP(t);
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/// To determine type of value stored in `Value`, you can use `Is` method:
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DUMP(a.Is<int>());
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DUMP(a.Is<double>());
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DUMP(b.Is<double>());
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DUMP(c.Is<int>());
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DUMP(c.Is<Date>());
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DUMP(d.Is<String>());
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/// Note that Is tests for absolute type match, not for compatible types. For that reason,
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/// for widely used compatible types helper functions are defined:
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DUMP(IsNumber(a));
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DUMP(IsNumber(b));
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DUMP(IsDateTime(c));
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DUMP(IsString(d));
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///
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} |