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Merge pull request #5749 from ethereum/docs-split-abstract

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[DOCS] Split Abstract Contracts docs to new file
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chriseth 2019-01-08 00:00:24 +01:00 committed by GitHub
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docs/contracts.rst
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@ -533,50 +533,7 @@ converted to ``uint8``.
.. include:: contracts/inheritance.rst
.. index:: ! contract;abstract, ! abstract contract
.. _abstract-contract:
******************
Abstract Contracts
******************
Contracts are marked as abstract when at least one of their functions lacks an implementation as in the following example (note that the function declaration header is terminated by ``;``)::
pragma solidity >=0.4.0 <0.6.0;
contract Feline {
function utterance() public returns (bytes32);
}
Such contracts cannot be compiled (even if they contain implemented functions alongside non-implemented functions), but they can be used as base contracts::
pragma solidity >=0.4.0 <0.6.0;
contract Feline {
function utterance() public returns (bytes32);
}
contract Cat is Feline {
function utterance() public returns (bytes32) { return "miaow"; }
}
If a contract inherits from an abstract contract and does not implement all non-implemented functions by overriding, it will itself be abstract.
Note that a function without implementation is different from a :ref:`Function Type <function_types>` even though their syntax looks very similar.
Example of function without implementation (a function declaration)::
function foo(address) external returns (address);
Example of a Function Type (a variable declaration, where the variable is of type ``function``)::
function(address) external returns (address) foo;
Abstract contracts decouple the definition of a contract from its implementation providing better extensibility and self-documentation and
facilitating patterns like the `Template method <https://en.wikipedia.org/wiki/Template_method_pattern>`_ and removing code duplication.
Abstract contracts are useful in the same way that defining methods in an interface is useful. It is a way for the designer of the abstract contract to say "any child of mine must implement this method".
.. include:: contracts/abstract-contracts.rst
.. index:: ! contract;interface, ! interface contract

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docs/contracts/abstract-contracts.rst Normal file
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.. index:: ! contract;abstract, ! abstract contract
.. _abstract-contract:
******************
Abstract Contracts
******************
Contracts are marked as abstract when at least one of their functions lacks an implementation as in the following example (note that the function declaration header is terminated by ``;``)::
pragma solidity >=0.4.0 <0.6.0;
contract Feline {
function utterance() public returns (bytes32);
}
Such contracts cannot be compiled (even if they contain implemented functions alongside non-implemented functions), but they can be used as base contracts::
pragma solidity >=0.4.0 <0.6.0;
contract Feline {
function utterance() public returns (bytes32);
}
contract Cat is Feline {
function utterance() public returns (bytes32) { return "miaow"; }
}
If a contract inherits from an abstract contract and does not implement all non-implemented functions by overriding, it will itself be abstract.
Note that a function without implementation is different from a :ref:`Function Type <function_types>` even though their syntax looks very similar.
Example of function without implementation (a function declaration)::
function foo(address) external returns (address);
Example of a Function Type (a variable declaration, where the variable is of type ``function``)::
function(address) external returns (address) foo;
Abstract contracts decouple the definition of a contract from its implementation providing better extensibility and self-documentation and
facilitating patterns like the `Template method <https://en.wikipedia.org/wiki/Template_method_pattern>`_ and removing code duplication.
Abstract contracts are useful in the same way that defining methods in an interface is useful. It is a way for the designer of the abstract contract to say "any child of mine must implement this method".