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74 lines
2.4 KiB
Markdown
74 lines
2.4 KiB
Markdown
## ERC20
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<br>
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* The ERC20 standard defines a common interface for contracts implementing this token, such that any compatible token can be accessed and used in the same way.
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<br>
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### ERC20-compliant token contract
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* totalSupply
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Returns the total units of this token that currently exist. ERC20 tokens can have a fixed or a variable supply.
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* balanceOf
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Given an address, returns the token balance of that address.
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* transfer
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Given an address and amount, transfers that amount of tokens to that address, from the balance of the address that executed the transfer.
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* transferFrom
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Given a sender, recipient, and amount, transfers tokens from one account to another. Used in combination with approve.
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* approve
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Given a recipient address and amount, authorizes that address to execute several transfers up to that amount, from the account that issued the approval.
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* allowance
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Given an owner address and a spender address, returns the remaining amount that the spender is approved to withdraw from the owner.
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* Transfer
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Event triggered upon a successful transfer (call to transfer or transferFrom) (even for zero-value transfers).
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* Approval
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Event logged upon a successful call to approve.
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<br>
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---
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### ERC20 optional functions
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In addition to the required functions listed in the previous section, the following optional functions are also defined by the standard:
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* name
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Returns the human-readable name (e.g., "US Dollars") of the token.
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* symbol
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Returns a human-readable symbol (e.g., "USD") for the token.
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* decimals
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Returns the number of decimals used to divide token amounts. For example, if decimals is 2, then the token amount is divided by 100 to get its user representation.
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<br>
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---
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### The ERC20 interface defined in Solidity
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```
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contract ERC20 {
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function totalSupply() constant returns (uint theTotalSupply);
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function balanceOf(address _owner) constant returns (uint balance);
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function transfer(address _to, uint _value) returns (bool success);
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function transferFrom(address _from, address _to, uint _value) returns
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(bool success);
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function approve(address _spender, uint _value) returns (bool success);
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function allowance(address _owner, address _spender) constant returns
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(uint remaining);
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event Transfer(address indexed _from, address indexed _to, uint _value);
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event Approval(address indexed _owner, address indexed _spender, uint _value);
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}
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```
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