Update common-patterns.rst

1 files changed, 44 insertions, 60 deletions

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));
         }
     }