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| -rw-r--r-- | docs/contracts.rst | 56 |
1 files changed, 47 insertions, 9 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst index 3ee98937..4372c278 100644 --- a/docs/contracts.rst +++ b/docs/contracts.rst @@ -194,17 +194,38 @@ return parameter list for functions. function setData(uint a) internal { data = a; } uint public data; } + +An other contract ``D`` can call ``c.getData()`` to retrieve the value of data in state +storage and is not able to call ``f``. Contract ``E`` is derived from ``C`` and can call +``compute``. + +:: + + contract C { + function f(uint a) private returns(uint b) { return a + 1; } + function setData(uint a) { data = a; } + function getData() public returns(uint) {return data;} + function compute(uint a, uint b) internal returns (uint) { return a+b;} + uint private data; + } + contract D { - function readData(){ - C c = new C(); - uint local = c.data(); - local = f(7); // error + function readData() { + C c = new C(); + local = c.f(7); // error: member "f" is not visible + c.setData(3); + uint local = c.getData(); + local = c.compute(3,5); // error: member "compute" is not visible + } + } + + contract E is C { + function g() { + C c = new C(); + uint val = compute(3,5); // acces to internal member (from derivated to parent contract) } } -An other contract ``D`` can call ``c.data()`` to retrieve the value of data in state -storage, is not able to call ``f``. Contracts derived from ``C`` can call -``setData`` to alter the value of ``data`` (but only in their own state). .. index:: ! accessor;function, ! function;accessor @@ -218,6 +239,19 @@ arguments and returns a ``uint``, the value of the state variable ``data``. The initialization of state variables can be done at declaration. +:: + + contract C { + uint public data = 42; + } + + contract Caller { + C c = new C(); + function f() { + uint local = c.data(); + } + } + The accessor functions have external visibility. If the symbol is accessed internally (i.e. without ``this.``), it is evaluated as state variable and if it is accessed externally @@ -225,8 +259,12 @@ it is evaluated as state variable and if it is accessed externally :: - contract Test { - uint public data = 42; + contract C { + uint public data; + function x() { + data = 3; // internal access + uint val = this.data(); // external access + } } The next example is a bit more complex: |