# Why we add \`onlyInitializer\` to internal functions? **URL:** \ **Category:** Smart Contracts\ **Created:** [April 17, 2024, 6:00pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250 "2024-04-17T18:00:29Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![poslednaya](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/poslednaya/32/20797_2.png) [@poslednaya](https://forum.openzeppelin.com/u/poslednaya)\ **Post date:** [April 17, 2024, 6:00pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/1 "2024-04-17T18:00:29Z")
q I'm trying to understand and I'm stuck, can u explain logic pls? For example I have some contracts and want to inherit them in one when deploying. ```solidity contract A { 1 function __A_init() internal {...} 2 function __A_init() internal onlyInitializer {...}; contract B { 1 function __B_init() internal {...} 2 function __B_init() internal onlyInitializer {...} contract C is A, B { constructor() initializer {} function initialize(...) initializer { __A_init(); __B_init(); } } ``` I see codebases where devs use `onlyInitializer` modifier for `init()` functions in A and B contracts. But in some codebases devs don't use this modifier. Should we use it considering that `init()` functions are internal? What's the logic of this choice? I read docs/forum, but can catch it. Also in some codebases in constructor ppl use `disableInitializer()` instead of `initializer`. I assume that in this case we want to leave the opportunity reinitialize in future? ---
**Author:** ![ernestognw](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/ernestognw/32/18576_2.png) [@ernestognw](https://forum.openzeppelin.com/u/ernestognw)\ **Post date:** [April 17, 2024, 10:21pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/2 "2024-04-17T22:21:19Z")
Hi @poslednaya, Have you gone through our [Writing Upgradeable Contracts documentation](https://docs.openzeppelin.com/upgrades-plugins/1.x/writing-upgradeable)? I think most of these questions can be answered from there. ---
**Author:** ![poslednaya](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/poslednaya/32/20797_2.png) [@poslednaya](https://forum.openzeppelin.com/u/poslednaya)\ **Post date:** [April 17, 2024, 10:25pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/3 "2024-04-17T22:25:54Z")
yp, I read In examples there initialize functions are public so modifier is obvious But I can not imagine case when we need to use `onlyInitializer` with internal functions Thx for answer, anyway ---
**Author:** ![ernestognw](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/ernestognw/32/18576_2.png) [@ernestognw](https://forum.openzeppelin.com/u/ernestognw)\ **Post date:** [April 17, 2024, 10:31pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/4 "2024-04-17T22:31:53Z")
Right, all of the upgradeable contracts have an internal initializer that replaces the constructor for upgradeable contracts. However, when a contract is abstract (the majority of contracts in the library are abstract), the constructor behaves like an "internal initializer", this is why you need to do something like: ```auto abstract contract A { constructor(uint256 foo, bytes32 bar) {} } contract B is A { constructor(uint foo, bytes32 bar) A(foo, bar) {} } ``` The upgradeable variant of the library exposes these internal initializers to replicate the behavior of abstract constructors. ---
**Author:** ![poslednaya](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/poslednaya/32/20797_2.png) [@poslednaya](https://forum.openzeppelin.com/u/poslednaya)\ **Post date:** [April 17, 2024, 10:47pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/5 "2024-04-17T22:47:08Z")
I got it. Sorry for inability to formulate a question. I'm looking at the code base right now. They have 2 contracts (not abstract) and then inherits in third. And I can not catch why absence of `onlyInitializing` is not a mistake. They literally rely on just `internal`, but in all examples in OpenZeppelin docs I see that modifier also is needed. ```solidity contract A { function __A_init() internal {...} // here without modifier contract B { function __B_init() internal {...} // here without modifier contract C is A, B { function initialize(...) initializer { __A_init(); __B_init(); } ``` I think I got how modifier works but can not understand why here it is not a mistake ---
**Author:** ![ernestognw](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/ernestognw/32/18576_2.png) [@ernestognw](https://forum.openzeppelin.com/u/ernestognw)\ **Post date:** [April 17, 2024, 10:54pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/6 "2024-04-17T22:54:58Z")
I see, that's weird. Unless those internal functions are not reachable within the external contract scope I guess it's fine, but I can't confirm it's safe to do so. The recommendation is to always use an `onlyInitializer` even if there's the need to reinitialize a contract. In such case, the `onlyInitializer` already takes reinitializations into account. ---
**Author:** ![poslednaya](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.openzeppelin.com/poslednaya/32/20797_2.png) [@poslednaya](https://forum.openzeppelin.com/u/poslednaya)\ **Post date:** [April 17, 2024, 10:59pm UTC](https://forum.openzeppelin.com/t/why-we-add-onlyinitializer-to-internal-functions/40250/7 "2024-04-17T22:59:56Z")
It would be better if this was a critical vulnerability and I shared the reward with you, but..) Thx a lot for your time, appreciate it, now it will more clear to me