What's the difference between onlyInitializing and initialzer?

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 function initialize(string memory name, string memory symbol, string memory baseURI_) external onlyInitializing {
        require(bytes(baseURI_).length>0, "Invalid BaseURI");
        __NFT__init(name, symbol, baseURI_);
    }

vs

 function initialize(string memory name, string memory symbol, string memory baseURI_) external initializer {
        require(bytes(baseURI_).length>0, "Invalid BaseURI");
        __NFT__init(name, symbol, baseURI_);
    }

Openzepplin Documentation reccomends using initailizer for initailizer functions (used instead for constructors in upgradable contract) while most of the upgradeable contract at @openzepplin/contracts-upgradeable use onlyInitializing.

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Hi @Richdevs,

As mentioned in the docs, your contracts can use the initializer modifier to prevent its initializer function from being invoked twice.

Whereas onlyInitializing protects an initialization function (e.g. a function that helps to initialize a parent library) so that it can only be invoked by functions with the initializer modifier, directly or indirectly.

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One way to understand it is that initializer is for public-facing functions, and onlyInitializing is protection for internal functions.

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