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47 lines
1.7 KiB
ReStructuredText
47 lines
1.7 KiB
ReStructuredText
###########################
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Frequently Asked Questions
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###########################
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This list was originally compiled by `fivedogit <mailto:fivedogit@gmail.com>`_.
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******************
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Advanced Questions
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******************
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Get return value from non-constant function from another contract
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=================================================================
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The key point is that the calling contract needs to know about the function it intends to call.
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See `ping.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/45_ping.sol>`_
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and `pong.sol <https://github.com/fivedogit/solidity-baby-steps/blob/master/contracts/45_pong.sol>`_.
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How do I initialize a contract with only a specific amount of wei?
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==================================================================
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Currently the approach is a little ugly, but there is little that can be done to improve it.
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In the case of a ``contract A`` calling a new instance of ``contract B``, parentheses have to be used around
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``new B`` because ``B.value`` would refer to a member of ``B`` called ``value``.
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You will need to make sure that you have both contracts aware of each other's presence and that ``contract B`` has a ``payable`` constructor.
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In this example::
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pragma solidity ^0.5.0;
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contract B {
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constructor() public payable {}
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}
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contract A {
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B child;
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function test() public {
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child = (new B).value(10)(); //construct a new B with 10 wei
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}
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}
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More Questions?
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===============
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If you have more questions or your question is not answered here, please talk to us on
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`gitter <https://gitter.im/ethereum/solidity>`_ or file an `issue <https://github.com/ethereum/solidity/issues>`_.
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