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authorMatt Wisniewski <contact.mattdylan@gmail.com>2017-04-20 02:12:45 +0800
committerchriseth <chris@ethereum.org>2017-05-03 18:03:02 +0800
commit2b4b86aa7f72d8f7c2c4e250953d8f9018f4fd53 (patch)
tree34b54c98a4e9f359479bbc5b73945b3c74884c98 /docs
parent00933b99cc64a5af1e00ed4b119fc725ddbb3513 (diff)
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Update common-patterns.rst
Diffstat (limited to 'docs')
-rw-r--r--docs/common-patterns.rst22
-rw-r--r--docs/contracts.rst19
-rw-r--r--docs/frequently-asked-questions.rst3
-rw-r--r--docs/security-considerations.rst11
-rw-r--r--docs/solidity-by-example.rst104
-rw-r--r--docs/structure-of-a-contract.rst4
-rw-r--r--docs/types.rst9
7 files changed, 73 insertions, 99 deletions
diff --git a/docs/common-patterns.rst b/docs/common-patterns.rst
index de2da690..37973c62 100644
--- a/docs/common-patterns.rst
+++ b/docs/common-patterns.rst
@@ -28,7 +28,7 @@ become the new richest.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract WithdrawalContract {
address public richest;
@@ -70,7 +70,7 @@ This is as opposed to the more intuitive sending pattern:
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract SendContract {
address public richest;
@@ -86,9 +86,7 @@ This is as opposed to the more intuitive sending pattern:
// Check if call succeeds to prevent an attacker
// from trapping the previous person's funds in
// this contract through a callstack attack
- if (!richest.send(msg.value)) {
- throw;
- }
+ richest.transfer(msg.value);
richest = msg.sender;
mostSent = msg.value;
return true;
@@ -135,7 +133,7 @@ restrictions highly readable.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract AccessRestriction {
// These will be assigned at the construction
@@ -152,8 +150,7 @@ restrictions highly readable.
// a certain address.
modifier onlyBy(address _account)
{
- if (msg.sender != _account)
- throw;
+ require(msg.sender == _account);
// Do not forget the "_;"! It will
// be replaced by the actual function
// body when the modifier is used.
@@ -169,7 +166,7 @@ restrictions highly readable.
}
modifier onlyAfter(uint _time) {
- if (now < _time) throw;
+ require(now >= _time);
_;
}
@@ -190,8 +187,7 @@ restrictions highly readable.
// This was dangerous before Solidity version 0.4.0,
// where it was possible to skip the part after `_;`.
modifier costs(uint _amount) {
- if (msg.value < _amount)
- throw;
+ require(msg.value >= _amount);
_;
if (msg.value > _amount)
msg.sender.send(msg.value - _amount);
@@ -276,7 +272,7 @@ function finishes.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract StateMachine {
enum Stages {
@@ -293,7 +289,7 @@ function finishes.
uint public creationTime = now;
modifier atStage(Stages _stage) {
- if (stage != _stage) throw;
+ require(stage == _stage);
_;
}
diff --git a/docs/contracts.rst b/docs/contracts.rst
index 26c0c886..a26d5a5e 100644
--- a/docs/contracts.rst
+++ b/docs/contracts.rst
@@ -327,7 +327,7 @@ inheritable properties of contracts and may be overridden by derived contracts.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract owned {
function owned() { owner = msg.sender; }
@@ -341,8 +341,7 @@ inheritable properties of contracts and may be overridden by derived contracts.
// function is executed and otherwise, an exception is
// thrown.
modifier onlyOwner {
- if (msg.sender != owner)
- throw;
+ require(msg.sender == owner);
_;
}
}
@@ -390,7 +389,7 @@ inheritable properties of contracts and may be overridden by derived contracts.
contract Mutex {
bool locked;
modifier noReentrancy() {
- if (locked) throw;
+ require(!locked);
locked = true;
_;
locked = false;
@@ -401,7 +400,7 @@ inheritable properties of contracts and may be overridden by derived contracts.
/// The `return 7` statement assigns 7 to the return value but still
/// executes the statement `locked = false` in the modifier.
function f() noReentrancy returns (uint) {
- if (!msg.sender.call()) throw;
+ require(msg.sender.call());
return 7;
}
}
@@ -989,7 +988,7 @@ more advanced example to implement a set).
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
library Set {
// We define a new struct datatype that will be used to
@@ -1035,8 +1034,7 @@ more advanced example to implement a set).
// The library functions can be called without a
// specific instance of the library, since the
// "instance" will be the current contract.
- if (!Set.insert(knownValues, value))
- throw;
+ assert(Set.insert(knownValues, value));
}
// In this contract, we can also directly access knownValues.flags, if we want.
}
@@ -1166,7 +1164,7 @@ available without having to add further code.
Let us rewrite the set example from the
:ref:`libraries` in this way::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
// This is the same code as before, just without comments
library Set {
@@ -1207,8 +1205,7 @@ Let us rewrite the set example from the
// corresponding member functions.
// The following function call is identical to
// Set.insert(knownValues, value)
- if (!knownValues.insert(value))
- throw;
+ require(knownValues.insert(value));
}
}
diff --git a/docs/frequently-asked-questions.rst b/docs/frequently-asked-questions.rst
index 639eb83e..029e32eb 100644
--- a/docs/frequently-asked-questions.rst
+++ b/docs/frequently-asked-questions.rst
@@ -665,8 +665,7 @@ What does the following strange check do in the Custom Token contract?
::
- if (balanceOf[_to] + _value < balanceOf[_to])
- throw;
+ require(balanceOf[_to] + _value >= balanceOf[_to]);
Integers in Solidity (and most other machine-related programming languages) are restricted to a certain range.
For ``uint256``, this is ``0`` up to ``2**256 - 1``. If the result of some operation on those numbers
diff --git a/docs/security-considerations.rst b/docs/security-considerations.rst
index 1e92afa7..f9ceed5d 100644
--- a/docs/security-considerations.rst
+++ b/docs/security-considerations.rst
@@ -79,7 +79,7 @@ outlined further below:
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract Fund {
/// Mapping of ether shares of the contract.
@@ -88,8 +88,7 @@ outlined further below:
function withdraw() {
var share = shares[msg.sender];
shares[msg.sender] = 0;
- if (!msg.sender.send(share))
- throw;
+ require(msg.sender.send(share));
}
}
@@ -162,7 +161,7 @@ Never use tx.origin for authorization. Let's say you have a wallet contract like
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
// THIS CONTRACT CONTAINS A BUG - DO NOT USE
contract TxUserWallet {
@@ -173,8 +172,8 @@ Never use tx.origin for authorization. Let's say you have a wallet contract like
}
function transfer(address dest, uint amount) {
- if (tx.origin != owner) { throw; }
- if (!dest.call.value(amount)()) throw;
+ require(tx.origin == owner);
+ require(dest.call.value(amount)());
}
}
diff --git a/docs/solidity-by-example.rst b/docs/solidity-by-example.rst
index 3d6221e4..a8e7eb2c 100644
--- a/docs/solidity-by-example.rst
+++ b/docs/solidity-by-example.rst
@@ -36,7 +36,7 @@ of votes.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
/// @title Voting with delegation.
contract Ballot {
@@ -87,14 +87,12 @@ of votes.
// Give `voter` the right to vote on this ballot.
// May only be called by `chairperson`.
function giveRightToVote(address voter) {
- if (msg.sender != chairperson || voters[voter].voted) {
- // `throw` terminates and reverts all changes to
- // the state and to Ether balances. It is often
- // a good idea to use this if functions are
- // called incorrectly. But watch out, this
- // will also consume all provided gas.
- throw;
- }
+ // `throw` terminates and reverts all changes to
+ // the state and to Ether balances. It is often
+ // a good idea to use this if functions are
+ // called incorrectly. But watch out, this
+ // will also consume all provided gas.
+ require(msg.sender == chairperson || !voters[voter].voted);
voters[voter].weight = 1;
}
@@ -102,12 +100,10 @@ of votes.
function delegate(address to) {
// assigns reference
Voter sender = voters[msg.sender];
- if (sender.voted)
- throw;
+ require(!sender.voted);
// Self-delegation is not allowed.
- if (to == msg.sender)
- throw;
+ require(to != msg.sender);
// Forward the delegation as long as
// `to` also delegated.
@@ -121,8 +117,7 @@ of votes.
to = voters[to].delegate;
// We found a loop in the delegation, not allowed.
- if (to == msg.sender)
- throw;
+ require(to != msg.sender);
}
// Since `sender` is a reference, this
@@ -145,8 +140,7 @@ of votes.
/// to proposal `proposals[proposal].name`.
function vote(uint proposal) {
Voter sender = voters[msg.sender];
- if (sender.voted)
- throw;
+ require(!sender.voted);
sender.voted = true;
sender.vote = proposal;
@@ -218,7 +212,7 @@ activate themselves.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract SimpleAuction {
// Parameters of the auction. Times are either
@@ -269,16 +263,16 @@ activate themselves.
// the transaction. The keyword payable
// is required for the function to
// be able to receive Ether.
- if (now > auctionStart + biddingTime) {
- // Revert the call if the bidding
- // period is over.
- throw;
- }
- if (msg.value <= highestBid) {
- // If the bid is not higher, send the
- // money back.
- throw;
- }
+
+ // Revert the call if the bidding
+ // period is over.
+ require(now < auctionStart + biddingTime);
+
+
+ // If the bid is not higher, send the
+ // money back.
+ require(msg.value <= highestBid);
+
if (highestBidder != 0) {
// Sending back the money by simply using
// highestBidder.send(highestBid) is a security risk
@@ -327,18 +321,15 @@ activate themselves.
// external contracts.
// 1. Conditions
- if (now <= auctionStart + biddingTime)
- throw; // auction did not yet end
- if (ended)
- throw; // this function has already been called
+ require(now >= auctionStart + biddingTime); // auction did not yet end
+ require(!ended); // this function has already been called
// 2. Effects
ended = true;
AuctionEnded(highestBidder, highestBid);
// 3. Interaction
- if (!beneficiary.send(highestBid))
- throw;
+ require(beneficiary.transfer(highestBid));
}
}
@@ -381,7 +372,7 @@ high or low invalid bids.
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract BlindAuction {
struct Bid {
@@ -409,8 +400,8 @@ high or low invalid bids.
/// functions. `onlyBefore` is applied to `bid` below:
/// The new function body is the modifier's body where
/// `_` is replaced by the old function body.
- modifier onlyBefore(uint _time) { if (now >= _time) throw; _; }
- modifier onlyAfter(uint _time) { if (now <= _time) throw; _; }
+ modifier onlyBefore(uint _time) { require(!now >= _time); _; }
+ modifier onlyAfter(uint _time) { require(!now <= _time); _; }
function BlindAuction(
uint _biddingTime,
@@ -454,13 +445,11 @@ high or low invalid bids.
onlyBefore(revealEnd)
{
uint length = bids[msg.sender].length;
- if (
- _values.length != length ||
- _fake.length != length ||
- _secret.length != length
- ) {
- throw;
- }
+ require(
+ _values.length == length ||
+ _fake.length == length ||
+ _secret.length == length
+ );
uint refund;
for (uint i = 0; i < length; i++) {
@@ -481,8 +470,7 @@ high or low invalid bids.
// the same deposit.
bid.blindedBid = 0;
}
- if (!msg.sender.send(refund))
- throw;
+ msg.sender.transfer(refund);
}
// This is an "internal" function which means that it
@@ -527,14 +515,12 @@ high or low invalid bids.
function auctionEnd()
onlyAfter(revealEnd)
{
- if (ended)
- throw;
+ require(!ended);
AuctionEnded(highestBidder, highestBid);
ended = true;
// We send all the money we have, because some
// of the refunds might have failed.
- if (!beneficiary.send(this.balance))
- throw;
+ beneficiary.transfer(this.balance);
}
}
@@ -546,7 +532,7 @@ Safe Remote Purchase
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract Purchase {
uint public value;
@@ -558,26 +544,26 @@ Safe Remote Purchase
function Purchase() payable {
seller = msg.sender;
value = msg.value / 2;
- if (2 * value != msg.value) throw;
+ require(!2 * value != msg.value);
}
modifier require(bool _condition) {
- if (!_condition) throw;
+ require(_condition);
_;
}
modifier onlyBuyer() {
- if (msg.sender != buyer) throw;
+ require(msg.sender == buyer);
_;
}
modifier onlySeller() {
- if (msg.sender != seller) throw;
+ require(msg.sender == seller);
_;
}
modifier inState(State _state) {
- if (state != _state) throw;
+ require(state == _state);
_;
}
@@ -594,8 +580,7 @@ Safe Remote Purchase
{
aborted();
state = State.Inactive;
- if (!seller.send(this.balance))
- throw;
+ seller.transfer(this.balance);
}
/// Confirm the purchase as buyer.
@@ -625,8 +610,7 @@ Safe Remote Purchase
state = State.Inactive;
// This actually allows both the buyer and the seller to
// block the refund.
- if (!buyer.send(value) || !seller.send(this.balance))
- throw;
+ require(buyer.transfer(value) || seller.transfer(this.balance));
}
}
diff --git a/docs/structure-of-a-contract.rst b/docs/structure-of-a-contract.rst
index 24ef69a6..224eb368 100644
--- a/docs/structure-of-a-contract.rst
+++ b/docs/structure-of-a-contract.rst
@@ -62,13 +62,13 @@ Function modifiers can be used to amend the semantics of functions in a declarat
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract Purchase {
address public seller;
modifier onlySeller() { // Modifier
- if (msg.sender != seller) throw;
+ require(msg.sender == seller);
_;
}
diff --git a/docs/types.rst b/docs/types.rst
index c868adc6..c400aecb 100644
--- a/docs/types.rst
+++ b/docs/types.rst
@@ -420,7 +420,7 @@ Example that shows how to use internal function types::
Another example that uses external function types::
- pragma solidity ^0.4.5;
+ pragma solidity ^0.4.11;
contract Oracle {
struct Request {
@@ -445,7 +445,7 @@ Another example that uses external function types::
oracle.query("USD", this.oracleResponse);
}
function oracleResponse(bytes response) {
- if (msg.sender != address(oracle)) throw;
+ require(msg.sender == address(oracle));
// Use the data
}
}
@@ -722,7 +722,7 @@ shown in the following example:
::
- pragma solidity ^0.4.0;
+ pragma solidity ^0.4.11;
contract CrowdFunding {
// Defines a new type with two fields.
@@ -763,8 +763,7 @@ shown in the following example:
return false;
uint amount = c.amount;
c.amount = 0;
- if (!c.beneficiary.send(amount))
- throw;
+ c.beneficiary.transfer(amount);
return true;
}
}