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43 lines
1.7 KiB
ReStructuredText
43 lines
1.7 KiB
ReStructuredText
.. highlight:: kotlin
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.. raw:: html
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<script type="text/javascript" src="_static/jquery.js"></script>
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<script type="text/javascript" src="_static/codesets.js"></script>
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Updating the contract
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=====================
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Remember that each state references a contract. The contract imposes constraints on transactions involving that state.
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If the transaction does not obey the constraints of all the contracts of all its states, it cannot become a valid
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ledger update.
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We need to modify our contract so that the borrower's signature is required in any IOU creation transaction. This will
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only require changing a single line of code. In ``IOUContract.java``/``IOUContract.kt``, update the final two lines of
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the ``requireThat`` block as follows:
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.. container:: codeset
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.. code-block:: kotlin
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// Constraints on the signers.
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"There must be two signers." using (command.signers.toSet().size == 2)
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"The borrower and lender must be signers." using (command.signers.containsAll(listOf(
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out.borrower.owningKey, out.lender.owningKey)))
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.. code-block:: java
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...
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import com.google.common.collect.ImmutableList;
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...
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// Constraints on the signers.
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check.using("There must be two signers.", command.getSigners().size() == 2);
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check.using("The borrower and lender must be signers.", command.getSigners().containsAll(
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ImmutableList.of(borrower.getOwningKey(), lender.getOwningKey())));
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Progress so far
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---------------
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Our contract now imposes an additional constraint - the borrower must also sign an IOU creation transaction. Next, we
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need to update ``IOUFlow`` so that it actually gathers the borrower's signature as part of the flow. |