1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
|
<!DOCTYPE html>
<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<title>test.sol</title>
<meta name="generator" content="KF5::SyntaxHighlighting - Definition (Solidity) - Theme (Breeze Light)"/>
</head><body style="background-color:#ffffff;color:#1f1c1b"><pre>
<span style="color:#898887">// Solidity Sample File</span>
<span style="color:#898887">// https://solidity.readthedocs.io/en/latest/solidity-by-example.html#voting</span>
<span style="font-weight:bold">pragma</span> <span style="color:#644a9b;font-weight:bold">solidity</span> >=0.4.22 <0.7.0;
<span style="color:#898887">/// </span><span style="color:#ca60ca">@title</span><span style="color:#898887"> Voting with delegation.</span>
<span style="font-weight:bold">contract</span> Ballot <span style="color:#ca60ca">{</span>
<span style="color:#898887">// This declares a new complex type which will</span>
<span style="color:#898887">// be used for variables later.</span>
<span style="color:#898887">// It will represent a single voter.</span>
<span style="font-weight:bold">struct</span> Voter <span style="color:#ca60ca">{</span>
<span style="color:#0057ae">uint</span> weight<span style="color:#ca60ca">;</span> <span style="color:#898887">// weight is accumulated by delegation</span>
<span style="color:#0057ae">bool</span> voted<span style="color:#ca60ca">;</span> <span style="color:#898887">// if true, that person already voted</span>
<span style="color:#0057ae">address</span> delegate<span style="color:#ca60ca">;</span> <span style="color:#898887">// person delegated to</span>
<span style="color:#0057ae">uint</span> vote<span style="color:#ca60ca">;</span> <span style="color:#898887">// index of the voted proposal</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">// This is a type for a single proposal.</span>
<span style="font-weight:bold">struct</span> Proposal <span style="color:#ca60ca">{</span>
<span style="color:#0057ae">bytes32</span> name<span style="color:#ca60ca">;</span> <span style="color:#898887">// short name (up to 32 bytes)</span>
<span style="color:#0057ae">uint</span> voteCount<span style="color:#ca60ca">;</span> <span style="color:#898887">// number of accumulated votes</span>
<span style="color:#ca60ca">}</span>
<span style="color:#0057ae">address</span> <span style="font-weight:bold">public</span> chairperson<span style="color:#ca60ca">;</span>
<span style="color:#898887">// This declares a state variable that</span>
<span style="color:#898887">// stores a `Voter` struct for each possible address.</span>
<span style="color:#0057ae">mapping</span><span style="color:#ca60ca">(</span><span style="color:#0057ae">address</span> <span style="color:#ca60ca">=></span> Voter<span style="color:#ca60ca">)</span> <span style="font-weight:bold">public</span> voters<span style="color:#ca60ca">;</span>
<span style="color:#898887">// A dynamically-sized array of `Proposal` structs.</span>
Proposal<span style="color:#ca60ca">[]</span> <span style="font-weight:bold">public</span> proposals<span style="color:#ca60ca">;</span>
<span style="color:#898887">/// Create a new ballot to choose one of `proposalNames`.</span>
<span style="font-weight:bold">constructor</span><span style="color:#ca60ca">(</span><span style="color:#0057ae">bytes32</span><span style="color:#ca60ca">[]</span> <span style="font-weight:bold">memory</span> proposalNames<span style="color:#ca60ca">)</span> <span style="font-weight:bold">public</span> <span style="color:#ca60ca">{</span>
chairperson <span style="color:#ca60ca">=</span> <span style="color:#644a9b;font-weight:bold">msg</span><span style="color:#ca60ca">.</span>sender<span style="color:#ca60ca">;</span>
voters<span style="color:#ca60ca">[</span>chairperson<span style="color:#ca60ca">].</span>weight <span style="color:#ca60ca">=</span> <span style="color:#b08000">1</span><span style="color:#ca60ca">;</span>
<span style="color:#898887">// For each of the provided proposal names,</span>
<span style="color:#898887">// create a new proposal object and add it</span>
<span style="color:#898887">// to the end of the array.</span>
<span style="font-weight:bold">for</span> <span style="color:#ca60ca">(</span><span style="color:#0057ae">uint</span> i <span style="color:#ca60ca">=</span> <span style="color:#b08000">0</span><span style="color:#ca60ca">;</span> i <span style="color:#ca60ca"><</span> proposalNames<span style="color:#ca60ca">.</span>length<span style="color:#ca60ca">;</span> i<span style="color:#644a9b;font-weight:bold">++</span><span style="color:#ca60ca">)</span> <span style="color:#ca60ca">{</span>
<span style="color:#898887">// `Proposal({...})` creates a temporary</span>
<span style="color:#898887">// Proposal object and `proposals.push(...)`</span>
<span style="color:#898887">// appends it to the end of `proposals`.</span>
proposals<span style="color:#ca60ca">.</span>push<span style="color:#ca60ca">(</span>Proposal<span style="color:#ca60ca">({</span>
name<span style="color:#ca60ca">:</span> proposalNames<span style="color:#ca60ca">[</span>i<span style="color:#ca60ca">],</span>
voteCount<span style="color:#ca60ca">:</span> <span style="color:#b08000">0</span>
<span style="color:#ca60ca">}));</span>
<span style="color:#ca60ca">}</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">// Give `voter` the right to vote on this ballot.</span>
<span style="color:#898887">// May only be called by `chairperson`.</span>
<span style="font-weight:bold">function</span> giveRightToVote<span style="color:#ca60ca">(</span><span style="color:#0057ae">address</span> voter<span style="color:#ca60ca">)</span> <span style="font-weight:bold">public</span> <span style="color:#ca60ca">{</span>
<span style="color:#898887">// If the first argument of `require` evaluates</span>
<span style="color:#898887">// to `false`, execution terminates and all</span>
<span style="color:#898887">// changes to the state and to Ether balances</span>
<span style="color:#898887">// are reverted.</span>
<span style="color:#898887">// This used to consume all gas in old EVM versions, but</span>
<span style="color:#898887">// not anymore.</span>
<span style="color:#898887">// It is often a good idea to use `require` to check if</span>
<span style="color:#898887">// functions are called correctly.</span>
<span style="color:#898887">// As a second argument, you can also provide an</span>
<span style="color:#898887">// explanation about what went wrong.</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(</span>
<span style="color:#644a9b;font-weight:bold">msg</span><span style="color:#ca60ca">.</span>sender <span style="color:#ca60ca">==</span> chairperson<span style="color:#ca60ca">,</span>
<span style="color:#bf0303">"Only chairperson can give right to vote."</span>
<span style="color:#ca60ca">);</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(</span>
<span style="color:#ca60ca">!</span>voters<span style="color:#ca60ca">[</span>voter<span style="color:#ca60ca">].</span>voted<span style="color:#ca60ca">,</span>
<span style="color:#bf0303">"The voter already voted."</span>
<span style="color:#ca60ca">);</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(</span>voters<span style="color:#ca60ca">[</span>voter<span style="color:#ca60ca">].</span>weight <span style="color:#ca60ca">==</span> <span style="color:#b08000">0</span><span style="color:#ca60ca">);</span>
voters<span style="color:#ca60ca">[</span>voter<span style="color:#ca60ca">].</span>weight <span style="color:#ca60ca">=</span> <span style="color:#b08000">1</span><span style="color:#ca60ca">;</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">/// Delegate your vote to the voter `to`.</span>
<span style="font-weight:bold">function</span> delegate<span style="color:#ca60ca">(</span><span style="color:#0057ae">address</span> to<span style="color:#ca60ca">)</span> <span style="font-weight:bold">public</span> <span style="color:#ca60ca">{</span>
<span style="color:#898887">// assigns reference</span>
Voter <span style="font-weight:bold">storage</span> sender <span style="color:#ca60ca">=</span> voters<span style="color:#ca60ca">[</span><span style="color:#644a9b;font-weight:bold">msg</span><span style="color:#ca60ca">.</span>sender<span style="color:#ca60ca">];</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(!</span>sender<span style="color:#ca60ca">.</span>voted<span style="color:#ca60ca">,</span> <span style="color:#bf0303">"You already voted."</span><span style="color:#ca60ca">);</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(</span>to <span style="color:#ca60ca">!=</span> <span style="color:#644a9b;font-weight:bold">msg</span><span style="color:#ca60ca">.</span>sender<span style="color:#ca60ca">,</span> <span style="color:#bf0303">"Self-delegation is disallowed."</span><span style="color:#ca60ca">);</span>
<span style="color:#898887">// Forward the delegation as long as</span>
<span style="color:#898887">// `to` also delegated.</span>
<span style="color:#898887">// In general, such loops are very dangerous,</span>
<span style="color:#898887">// because if they run too long, they might</span>
<span style="color:#898887">// need more gas than is available in a block.</span>
<span style="color:#898887">// In this case, the delegation will not be executed,</span>
<span style="color:#898887">// but in other situations, such loops might</span>
<span style="color:#898887">// cause a contract to get "stuck" completely.</span>
<span style="font-weight:bold">while</span> <span style="color:#ca60ca">(</span>voters<span style="color:#ca60ca">[</span>to<span style="color:#ca60ca">].</span>delegate <span style="color:#ca60ca">!=</span> <span style="color:#0057ae">address</span><span style="color:#ca60ca">(</span><span style="color:#b08000">0</span><span style="color:#ca60ca">))</span> <span style="color:#ca60ca">{</span>
to <span style="color:#ca60ca">=</span> voters<span style="color:#ca60ca">[</span>to<span style="color:#ca60ca">].</span>delegate<span style="color:#ca60ca">;</span>
<span style="color:#898887">// We found a loop in the delegation, not allowed.</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(</span>to <span style="color:#ca60ca">!=</span> <span style="color:#644a9b;font-weight:bold">msg</span><span style="color:#ca60ca">.</span>sender<span style="color:#ca60ca">,</span> <span style="color:#bf0303">"Found loop in delegation."</span><span style="color:#ca60ca">);</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">// Since `sender` is a reference, this</span>
<span style="color:#898887">// modifies `voters[msg.sender].voted`</span>
sender<span style="color:#ca60ca">.</span>voted <span style="color:#ca60ca">=</span> <span style="font-weight:bold">true</span><span style="color:#ca60ca">;</span>
sender<span style="color:#ca60ca">.</span>delegate <span style="color:#ca60ca">=</span> to<span style="color:#ca60ca">;</span>
Voter <span style="font-weight:bold">storage</span> delegate_ <span style="color:#ca60ca">=</span> voters<span style="color:#ca60ca">[</span>to<span style="color:#ca60ca">];</span>
<span style="font-weight:bold">if</span> <span style="color:#ca60ca">(</span>delegate_<span style="color:#ca60ca">.</span>voted<span style="color:#ca60ca">)</span> <span style="color:#ca60ca">{</span>
<span style="color:#898887">// If the delegate already voted,</span>
<span style="color:#898887">// directly add to the number of votes</span>
proposals<span style="color:#ca60ca">[</span>delegate_<span style="color:#ca60ca">.</span>vote<span style="color:#ca60ca">].</span>voteCount <span style="color:#ca60ca">+=</span> sender<span style="color:#ca60ca">.</span>weight<span style="color:#ca60ca">;</span>
<span style="color:#ca60ca">}</span> <span style="font-weight:bold">else</span> <span style="color:#ca60ca">{</span>
<span style="color:#898887">// If the delegate did not vote yet,</span>
<span style="color:#898887">// add to her weight.</span>
delegate_<span style="color:#ca60ca">.</span>weight <span style="color:#ca60ca">+=</span> sender<span style="color:#ca60ca">.</span>weight<span style="color:#ca60ca">;</span>
<span style="color:#ca60ca">}</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">/// Give your vote (including votes delegated to you)</span>
<span style="color:#898887">/// to proposal `proposals[proposal].name`.</span>
<span style="font-weight:bold">function</span> vote<span style="color:#ca60ca">(</span><span style="color:#0057ae">uint</span> proposal<span style="color:#ca60ca">)</span> <span style="font-weight:bold">public</span> <span style="color:#ca60ca">{</span>
Voter <span style="font-weight:bold">storage</span> sender <span style="color:#ca60ca">=</span> voters<span style="color:#ca60ca">[</span><span style="color:#644a9b;font-weight:bold">msg</span><span style="color:#ca60ca">.</span>sender<span style="color:#ca60ca">];</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(</span>sender<span style="color:#ca60ca">.</span>weight <span style="color:#ca60ca">!=</span> <span style="color:#b08000">0</span><span style="color:#ca60ca">,</span> <span style="color:#bf0303">"Has no right to vote"</span><span style="color:#ca60ca">);</span>
<span style="color:#644a9b;font-weight:bold">require</span><span style="color:#ca60ca">(!</span>sender<span style="color:#ca60ca">.</span>voted<span style="color:#ca60ca">,</span> <span style="color:#bf0303">"Already voted."</span><span style="color:#ca60ca">);</span>
sender<span style="color:#ca60ca">.</span>voted <span style="color:#ca60ca">=</span> <span style="font-weight:bold">true</span><span style="color:#ca60ca">;</span>
sender<span style="color:#ca60ca">.</span>vote <span style="color:#ca60ca">=</span> proposal<span style="color:#ca60ca">;</span>
<span style="color:#898887">// If `proposal` is out of the range of the array,</span>
<span style="color:#898887">// this will throw automatically and revert all</span>
<span style="color:#898887">// changes.</span>
proposals<span style="color:#ca60ca">[</span>proposal<span style="color:#ca60ca">].</span>voteCount <span style="color:#ca60ca">+=</span> sender<span style="color:#ca60ca">.</span>weight<span style="color:#ca60ca">;</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">/// </span><span style="color:#ca60ca">@dev</span><span style="color:#898887"> Computes the winning proposal taking all</span>
<span style="color:#898887">/// previous votes into account.</span>
<span style="font-weight:bold">function</span> winningProposal<span style="color:#ca60ca">()</span> <span style="font-weight:bold">public</span> <span style="font-weight:bold">view</span>
<span style="font-weight:bold">returns</span> <span style="color:#ca60ca">(</span><span style="color:#0057ae">uint</span> winningProposal_<span style="color:#ca60ca">)</span>
<span style="color:#ca60ca">{</span>
<span style="color:#0057ae">uint</span> winningVoteCount <span style="color:#ca60ca">=</span> <span style="color:#b08000">0</span><span style="color:#ca60ca">;</span>
<span style="font-weight:bold">for</span> <span style="color:#ca60ca">(</span><span style="color:#0057ae">uint</span> p <span style="color:#ca60ca">=</span> <span style="color:#b08000">0</span><span style="color:#ca60ca">;</span> p <span style="color:#ca60ca"><</span> proposals<span style="color:#ca60ca">.</span>length<span style="color:#ca60ca">;</span> p<span style="color:#644a9b;font-weight:bold">++</span><span style="color:#ca60ca">)</span> <span style="color:#ca60ca">{</span>
<span style="font-weight:bold">if</span> <span style="color:#ca60ca">(</span>proposals<span style="color:#ca60ca">[</span>p<span style="color:#ca60ca">].</span>voteCount <span style="color:#ca60ca">></span> winningVoteCount<span style="color:#ca60ca">)</span> <span style="color:#ca60ca">{</span>
winningVoteCount <span style="color:#ca60ca">=</span> proposals<span style="color:#ca60ca">[</span>p<span style="color:#ca60ca">].</span>voteCount<span style="color:#ca60ca">;</span>
winningProposal_ <span style="color:#ca60ca">=</span> p<span style="color:#ca60ca">;</span>
<span style="color:#ca60ca">}</span>
<span style="color:#ca60ca">}</span>
<span style="color:#ca60ca">}</span>
<span style="color:#898887">// Calls winningProposal() function to get the index</span>
<span style="color:#898887">// of the winner contained in the proposals array and then</span>
<span style="color:#898887">// returns the name of the winner</span>
<span style="font-weight:bold">function</span> winnerName<span style="color:#ca60ca">()</span> <span style="font-weight:bold">public</span> <span style="font-weight:bold">view</span>
<span style="font-weight:bold">returns</span> <span style="color:#ca60ca">(</span><span style="color:#0057ae">bytes32</span> winnerName_<span style="color:#ca60ca">)</span>
<span style="color:#ca60ca">{</span>
winnerName_ <span style="color:#ca60ca">=</span> proposals<span style="color:#ca60ca">[</span>winningProposal<span style="color:#ca60ca">()].</span>name<span style="color:#ca60ca">;</span>
<span style="color:#ca60ca">}</span>
<span style="color:#ca60ca">}</span>
</pre></body></html>
|
