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Due to frequent difficulties with building Murano PL blocks of code,
which beginners creating new applications have, block constructs
section was updated. Added info about using dashes in blocks.
Also, information about 'try-catch' construct was added.

Change-Id: I2aeab04abc6f2d358c3a964d8fe0209fab2975cc
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Dmytro Dovbii 2015-06-26 12:26:25 +03:00
parent ed6c26c8ca
commit 5838107f4b
1 changed files with 88 additions and 59 deletions
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147
doc/source/draft/appdev-guide/murano_pl/class_templ.rst
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@ -321,65 +321,94 @@ strings as all their keys.
The following block constructs are available: The following block constructs are available:
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| Assignment | Explanation | | Assignment | Explanation |
+=============================+=======================================================================================+ +===========================+=======================================================================================+
| | Return: value | | returns value from a method | | | Return: value | | Returns value from a method |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | If: predicate() | | ``predicate()`` is a YAQL expression that must be evaluated to ``True`` or ``False``| | | If: predicate() | | ``predicate()`` is a YAQL expression that must be evaluated to ``True`` or ``False``|
| | Then: | | | | Then: | |
| | - code | | The ``Else`` section is optional | | | - code | | The ``Else`` section is optional |
| | - block | | One-line code blocks can be written as scalars rather than an array. | | | - block | | One-line code blocks can be written as scalars rather than an array. |
| | Else: | | | | Else: | |
| | - code | | | | - code | |
| | - block | | | | - block | |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | While: predicate() | | ``predicate()`` must be evaluated to ``True`` or ``False`` | | | While: predicate() | | ``predicate()`` must be evaluated to ``True`` or ``False`` |
| | Do: | | | | Do: | |
| | - code | | | | - code | |
| | - block | | | | - block | |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | For: variableName | | ``collection`` must be a YAQL expression returning iterable collection or | | | For: variableName | | ``collection`` must be a YAQL expression returning iterable collection or |
| | In: collection | evaluatable array as in assignment instructions, for example, ``[1, 2, $x]`` | | | In: collection | evaluatable array as in assignment instructions, for example, ``[1, 2, $x]`` |
| | Do: | | | | Do: | |
| | - code | | Inside a code block loop, a variable is accessible as ``$variableName`` | | | - code | | Inside a code block loop, a variable is accessible as ``$variableName`` |
| | - block | | | | - block | |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | Repeat: | | Repeats the code block specified number of times | | | Repeat: | | Repeats the code block specified number of times |
| | Do: | | | | Do: | |
| | - code | | | | - code | |
| | - block | | | | - block | |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | Break: | | Breaks from loop | | | Break: | | Breaks from loop |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | Match: | | Matches the result of ``$valueExpression()`` against a set of possible values | | | Match: | | Matches the result of ``$valExpression()`` against a set of possible values |
| | case1: | (cases). The code block of first matched case is executed. | | | case1: | (cases). The code block of first matched case is executed. |
| | - code | | | | - code | |
| | - block | | If no case matched and the default key is present | | | - block | | If no case matched and the default key is present |
| | case2: | than the ``Default`` code block get executed. | | | case2: | than the ``Default`` code block get executed. |
| | - code | | The case values are constant values (not expressions). | | | - code | | The case values are constant values (not expressions). |
| | - block | | | | - block | |
| | Value: $valueExpression() | | | | Value: $valExpression() | |
| | Default: | | | | Default: | |
| | - code | | | | - code | |
| | - block | | | | - block | |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | Switch: | | All code blocks that have their predicate evaluated to ``True`` are executed, | | | Switch: | | All code blocks that have their predicate evaluated to ``True`` are executed, |
| | $predicate1() : | but the order of predicate evaluation is not fixed. | | | $predicate1(): | but the order of predicate evaluation is not fixed. |
| | - code | | | | - code | |
| | - block | | | | - block | |
| | $predicate2() : | | | | $predicate2(): | |
| | - code | | | | - code | |
| | - block | | | | - block | |
| | Default: | | The ``Default`` key is optional. | | | Default: | | The ``Default`` key is optional. |
| | - code | | | | - code | |
| | - block | | If no predicate evaluated to ``True``, the ``Default`` code block get executed. | | | - block | | If no predicate evaluated to ``True``, the ``Default`` code block get executed. |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | Parallel: | | Executes all instructions in code block in a separate green threads in parallel. | | | Parallel: | | Executes all instructions in code block in a separate green threads in parallel. |
| | - code | | | | - code | |
| | - block | | | | - block | |
| | Limit: 5 | | The limit is optional and means the maximum number of concurrent green threads. | | | Limit: 5 | | The limit is optional and means the maximum number of concurrent green threads. |
+-----------------------------+---------------------------------------------------------------------------------------+ +---------------------------+---------------------------------------------------------------------------------------+
| | Try: | | Try and Catch are keywords that represent the handling of exceptions due to data |
| | - code | or coding errors during program execution. A ``Try`` block is the block of code in |
| | - block | which exceptions occur. A ``Catch`` block is the block of code, that is executed if |
| | Catch: | an exception occurred. |
| | With: keyError | | Exceptions are not declared in Murano PL. It means that exceptions of any types can |
| | As: e | be handled and generated. Generating of exception can be done with construct: |
| | Do: | ``Throw: keyError``. |
| | - code | |
| | - block | |
| | Else: | | The ``Else`` is optional block. ``Else`` block is executed if no exception occurred.|
| | - code | |
| | - block | |
| | Finally: | | The ``Finally`` also is optional. It's a place to put any code that will |
| | - code | be executed, whether the try-block raised an exception or not. |
| | - block | |
+---------------------------+---------------------------------------------------------------------------------------+
Notice, that if you have more then one block construct in your workflow, you
need to insert dashes before each construct. For example::
Body:
- If: predicate1()
Then:
- code
- block
- While: predicate2()
Do:
- code
- block
Object model Object model
------------ ------------