Example contracts

wemeetagain · March 2014

For me, examples are always very helpful. I feel like I haven't seen that many contract examples...
Lets try to make some basic examples.

I'll start.

A nameserver, where only the sender can edit the data created by that sender:


// input: tx.data[0] = name, tx.data[1] = name data
// stores: key: name, value: [owner address, name data]

// if the fee isn't large enough to run the contract, stop
if tx.value < 100 * block.basefee:
stop
// if the name can overwrite the contract code, stop
if tx.data[0] < 100:
stop
// if name already exists and the sender isn't the name owner, stop
if contract.storage[tx.data[0]]:
if contract.storage[tx.data[0]][0] != tx.sender:
stop
// set name owner and associated data
a = array()
a[0] = tx.sender
a[1] = tx.data[1]
contract.storage[tx.data[0]] = a

wemeetagain · March 2014

Ok, lets make that contract a bit better. Lets add the ability to swap the 'owner' of the name to another address.


// input: tx.data[0] = name, tx.data[1] = name data, tx.data[2] = new owner (optional)
// stores: key: name, value: [owner address (or new owner), name data]

// if the fee isn't large enough to run the contract, stop
if tx.value < 100 * block.basefee:
stop
// if the name can overwrite the contract code, stop
if tx.data[0] < 100:
stop
// if name already exists and the sender isn't the name owner, stop
if contract.storage[tx.data[0]]:
if contract.storage[tx.data[0]][0] != tx.sender:
stop
// set name owner and associated data
a = array()
// if the new owner has been specified, store as owner
if tx.data[2] != 0:
a[0] = tx.data[2]
else:
a[0] = tx.sender
a[1] = tx.data[1]
contract.storage[tx.data[0]] = a