Ethereum solidity internal vs external functions

Those keywords can be used for variables and functions. However, in some cases they behave a bit differently. This function is described in the ABI so that user interfaces can easily access the content of the variable. Public also means that the owner contract, EOAs, and other contracts have read access to the variable. If a function is set to public, EOAs, other contracts, derived contracts, and the owner contract can invoke it.

They are part of the contract interface. Other contracts, derived contracts, and EOAs have no access. Internal Internal state variables and functions are visible and accessible by the owner contract and derived contracts. Other contracts and EOAs have no right to access them. Functions can be specified as being external, public, internal or private. Please understand the differences between them, for example, external may be sufficient instead of public.

For state variables, external is not possible. Labeling the visibility explicitly will make it easier to catch incorrect assumptions about who can call the function or access the variable. External functions are part of the contract interface.

An external function f cannot be called internally i.

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Feb 12 at 1 AlirezaZojaji String is effectively a dynamic-length array of bytes. And Solidity allows for dynamic-length array without predefined size. Its selector 0xf31a is then calculated from the function name and types without the memory data location : foo string Feb 12 at 1 AlirezaZojaji If a param is a dynamic-sized array, its value consists of 2 parts: 1 pointer to the location of the actual value, and 2 the actual value.

Example: When you callfoo string,string , you pass at least four byte slots of data. If the first string was longer than one slot - for example 3 slots - the second string starts in and the second pointer points to a slot after these three. Memory allocation is expensive, whereas reading from calldata is cheap. The reason that public functions need to write all of the arguments to memory is that public functions may be called internally, which is actually an entirely different process than external calls.

Internal calls are executed via jumps in the code, and array arguments are passed internally by pointers to memory. Thus, when the compiler generates the code for an internal function, that function expects its arguments to be located in memory. For external functions, the compiler doesn't need to allow internal calls, and so it allows arguments to be read directly from calldata, saving the copying step. As for best practices, you should use external if you expect that the function will only ever be called externally, and use public if you need to call the function internally.