Explain an ABI.
The JSON ABI Format is the format that is output from the Solidity compiler.
A JSON serialized object is always a string, which represents an Array of Objects, where each Object has various properties describing the Fragment of the ABI.
The deserialied JSON string (which is a normal JavaScript Object) may also be passed into any function which accepts a JSON String ABI.
The Human-Readable ABI was
Output Formats
Each Fragment and ParamType may be output using its format method.
This is a full human-readable string, including all parameter names, any optional modifiers (e.g. indexed, public, etc) and white-space to aid in human readabiliy.
This is similar to full, except with no unnecessary whitespace or parameter names. This is useful for storing a minimal string which can still fully reconstruct the original Fragment using Fragment . from.
This returns a JavaScript Object which is safe to call JSON.stringify on to create a JSON string.
This is a minimal output format, which is used by Solidity when computing a signature hash or an event topic hash.
The sighash format is insufficient to re-create the original Fragment, since it discards modifiers such as indexed, anonymous, stateMutability, etc.
Fragment
An ABI is a collection of Fragments, where each fragment specifies:
- An Event
- A Function
- A Constructor
This is the name of the Event or Function. This will be null for a ConstructorFragment.
This is a string which indicates the type of the Fragment. This will be one of:
constructoreventfunction
This is an array of of each ParamType for the input parameters to the Constructor, Event of Function.
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This is the gas limit that should be used during deployment. It may be null.
This is whether the constructor may receive ether during deployment as an endowment (i.e. msg.value != 0).
This is the state mutability of the constructor. It can be any of:
nonpayablepayable
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This is whether the event is anonymous. An anonymous Event does not inject its topic hash as topic0 when creating a log.
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FunctionFragment inherits ConstructorFragment
This is whether the function is constant (i.e. does not change state). This is true if the state mutability is pure or view.
This is the state mutability of the constructor. It can be any of:
nonpayablepayablepureview
A list of the Function output parameters.
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ParamType
The following examples will represent the Solidity parameter:
string foobar
The local parameter name. This may be null for unnamed parameters. For example, the parameter definition string foobar would be foobar.
The full type of the parameter, including tuple and array symbols. This may be null for unnamed parameters. For the above example, this would be foobar.
The base type of the parameter. For primitive types (e.g. address, uint256, etc) this is equal to type. For arrays, it will be the string array and for a tuple, it will be the string tuple.
Whether the parameter has been marked as indexed. This only applies to parameters which are part of an EventFragment.
The type of children of the array. This is null for for any parameter wjhich is not an array.
The length of the array, or -1 for dynamic-length arrays. This is null for parameters which is not arrays.
The components of a tuple. This is null for non-tuple parameters.
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