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@@ -57,6 +57,7 @@
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<a href="#classof">Translating class-of type</a><br>
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<a href="#tobjectfree">Translating TObject.Free</a><br>
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<a href="#classinterfaces">Translating class interfaces</a><br>
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+ <a href="#helpers">Translating helpers</a><br>
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<a href="#attributes">Translating attributes</a><br>
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<a href="#tryfinally">Translating try..finally</a><br>
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<a href="#tryexcept">Translating try..except</a><br>
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@@ -1831,6 +1832,80 @@ function(){
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Not yet supported: array of intferfacetype, interface as record member.
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</div>
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+ <div class="section">
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+ <h2 id="helpers">Translating helpers</h2>
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+ Pas2js supports class helpers, record helpers and type helpers.
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+ The extend is only virtual, the helped type is kept untouched.
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+ <br>
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+ <ul>
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+ <li>A <b>class helper</b> can "extend" Pascal classes and external JS classes.</li>
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+ <li>A <b>record helper</b> can "extend" a record type. In $mode delphi a
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+ record helper can extend other types as well, see <i>type helper</i></li>
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+ <li>A <b>type helper</b> can extend all base types like integer, string,
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+ char, boolean, double, currency, and some user types like enumeration,
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+ set, range and array types. It cannot extend interfaces or helpers.<br>
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+ Type helpers are enabled by default in <i>$mode delphi</i> and disabled in <i>$mode objfpc</i>.
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+ You can enable them with <b>{$modeswitch typehelpers}</b>.
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+ </li>
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+ <li>By default only one helper is active per type, same as in FPC/Delphi.
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+ If there are multiple helpers for the same type, the last helper in scope wins.<br>
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+ A class with ancestors can have one active helper per ancestor type, so
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+ multiple helpers can be active, same as FPC/Delphi.<br>
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+ Using <b>{$modeswitch multiplescopehelpers}</b> you can activate all helpers
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+ within scope.
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+ </li>
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+ <li>Nested helpers (e.g. <i>TDemo.TSub.THelper</i>) are elevated.
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+ Visibility is ignored. Same as FPC/Delphi.</li>
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+ <li>Helpers cannot be forward defined (e.g. no <i>THelper = helper;</i>).</li>
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+ <li>Helpers must not have fields.</li>
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+ <li><b>Class Var, Const, Type</b></li>
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+ <li><b>Visibility</b>: <i>strict private .. published</i></li>
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+ <li><b>Function, procedure</b>:
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+ In class and record helpers <i>Self</i> is the class/record instance. For other
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+ types Self is a reference to the passed value.
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+ </li>
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+ <li><b>Class function, class procedure</b>: Helpers for Pascal classes/records can
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+ add <i>static</i> and non static class functions. Helpers for external classes
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+ and other types can only add static class functions.</li>
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+ <li><b>Constructor</b>. Not for external classes. Works similar to
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+ construcors, i.e. <i>THelpedClass.Create</i> creates a new instance, while
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+ <i>AnObj.Create</i> calls the constructor function as normal method. Note that
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+ Delphi does not allow calling helper construcors as normal method.</li>
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+ <li>no destructor</li>
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+ <li><b>Property</b>: getters/setters can refer to members of the helper, its
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+ ancestors and the helped class/record.</li>
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+ <li><b>Class property</b>: getter can be static or non static. Delphi/FPC only allows static.</li>
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+ <li><b>Ancestors</b>. Helpers can have an ancestor helper, but they
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+ do not have a shared root class, especially not <i>TObject</i>.</li>
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+ <li><b>no virtual, abstract, override</b>. Delphi allows them, but 10.3 crashes when calling.</li>
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+ <li><b>inherited</b>:
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+ <i>inherited</i> inside a method of a class/record calls helper of ancestor.<br>
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+ <i>inherited</i> inside a helper depends on the $mode:
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+ <ul>
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+ <li> <i>$mode objfpc</i>: <i>inherited;</i> and <i>inherited Name(args);</i>
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+ work the same and searches first in HelperForType, then in ancestor(s).</li>
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+ <li><i>$mode delphi: inherited;</i>: skip ancestors and HelperForType,
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+ searches first in helper(s) of ancestor of HelperForType.</li>
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+ <li><i>$mode delphi: inherited name(args);</i>:
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+ same as $mode objfpc first searches in HelperForType, then Ancestor(s)</li>
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+ </ul>
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+ In any case if <i>inherited;</i> has no ancestor to call, it is silently ignored,
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+ while <i>inherited Name;</i> gives an error.
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+ </li>
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+ <li><b>RTTI</b>: <i>typeinfo(somehelper)</i> returns a pointer to <i>TTypeInfoHelper</i> with <i>Kind tkHelper</i>.</li>
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+ <li>There are some special cases when using a <b>type helper</b> function/procedure on a value:
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+ <ul>
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+ <li><i>function result</i>: using a temporary variable</li>
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+ <li><i>const, const argument</i>: When helper function tries to assign a value,
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+ pas2js raises a EPropReadOnly exception. FPC/Delphi use a temporary variable allowing the write. </li>
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+ <li><i>property</i>: uses only the getter, ignoring the setter.
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+ This breaks OOP, as it allows to change fields without calling the setter.
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+ This is FPC/Delphi compatible.</li>
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+ </ul>
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+ </li>
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+ </ul>
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+ </div>
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+
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<div class="section">
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<h2 id="attributes">Translating attributes</h2>
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Attributes are not yet implemented. To make porting code easier there
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@@ -3003,15 +3078,13 @@ End.
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<div class="section">
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<h2 id="notsupportedelements">Not supported elements</h2>
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<ul>
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- <li>Advanced records</li>
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- <li>Anonymous functions</li>
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<li>Array of const</li>
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<li>Attributes</li>
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+ <li>Class constructor, class destructor</li>
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<li>Enums with custom values</li>
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<li>Generics</li>
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<li>Global properties</li>
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<li>Futures</li>
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- <li>Helpers for types, classes, records</li>
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<li>Inline</li>
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<li>Library</li>
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<li>Objects</li>
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Mattias Gaertner