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Merge pull request #12467 from ethereum/fixMappingExample

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Fix mapping example.
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Daniel Kirchner 2022-01-04 18:23:57 +01:00 committed by GitHub
commit cac0f203a2
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1 changed files with 6 additions and 5 deletions
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docs/types/mapping-types.rst
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@ -84,23 +84,24 @@ The example below uses ``_allowances`` to record the amount someone else is allo
}
function transferFrom(address sender, address recipient, uint256 amount) public returns (bool) {
require(_allowances[sender][msg.sender] >= amount, "ERC20: Allowance not high enough.");
_allowances[sender][msg.sender] -= amount;
_transfer(sender, recipient, amount);
approve(sender, msg.sender, amount);
return true;
}
function approve(address owner, address spender, uint256 amount) public returns (bool) {
require(owner != address(0), "ERC20: approve from the zero address");
function approve(address spender, uint256 amount) public returns (bool) {
require(spender != address(0), "ERC20: approve to the zero address");
_allowances[owner][spender] = amount;
emit Approval(owner, spender, amount);
_allowances[msg.sender][spender] = amount;
emit Approval(msg.sender, spender, amount);
return true;
}
function _transfer(address sender, address recipient, uint256 amount) internal {
require(sender != address(0), "ERC20: transfer from the zero address");
require(recipient != address(0), "ERC20: transfer to the zero address");
require(_balances[sender] >= amount, "ERC20: Not enough funds.");
_balances[sender] -= amount;
_balances[recipient] += amount;