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Move String literal and inline array FAQ items
Fix tab Update docs/types.rst Co-Authored-By: ChrisChinchilla <chriswhward@gmail.com> Update docs/types.rst Co-Authored-By: ChrisChinchilla <chriswhward@gmail.com>
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@ -38,24 +38,6 @@ has it (which includes `Remix <https://remix.ethereum.org/>`_), then
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``contractname.kill.sendTransaction({from:eth.coinbase})``, just the same as my
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``contractname.kill.sendTransaction({from:eth.coinbase})``, just the same as my
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examples.
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examples.
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Is it possible to in-line initialize an array like so: ``string[] myarray = ["a", "b"];``
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=========================================================================================
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Yes. However it should be noted that this currently only works with statically sized memory arrays. You can even create an inline memory
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array in the return statement.
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Example::
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pragma solidity >=0.4.16 <0.6.0;
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contract C {
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function f() public pure returns (uint8[5] memory) {
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string[4] memory adaArr = ["This", "is", "an", "array"];
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adaArr[0] = "That";
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return [1, 2, 3, 4, 5];
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}
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}
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If I return an ``enum``, I only get integer values in web3.js. How to get the named values?
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If I return an ``enum``, I only get integer values in web3.js. How to get the named values?
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===========================================================================================
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===========================================================================================
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@ -217,28 +199,6 @@ In this example::
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}
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}
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}
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}
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What is the relationship between ``bytes32`` and ``string``? Why is it that ``bytes32 somevar = "stringliteral";`` works and what does the saved 32-byte hex value mean?
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========================================================================================================================================================================
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The type ``bytes32`` can hold 32 (raw) bytes. In the assignment ``bytes32 samevar = "stringliteral";``,
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the string literal is interpreted in its raw byte form and if you inspect ``somevar`` and
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see a 32-byte hex value, this is just ``"stringliteral"`` in hex.
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The type ``bytes`` is similar, only that it can change its length.
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Finally, ``string`` is basically identical to ``bytes`` only that it is assumed
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to hold the UTF-8 encoding of a real string. Since ``string`` stores the
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data in UTF-8 encoding it is quite expensive to compute the number of
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characters in the string (the encoding of some characters takes more
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than a single byte). Because of that, ``string s; s.length`` is not yet
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supported and not even index access ``s[2]``. But if you want to access
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the low-level byte encoding of the string, you can use
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``bytes(s).length`` and ``bytes(s)[2]`` which will result in the number
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of bytes in the UTF-8 encoding of the string (not the number of
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characters) and the second byte (not character) of the UTF-8 encoded
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string, respectively.
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Can a contract pass an array (static size) or string or ``bytes`` (dynamic size) to another contract?
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Can a contract pass an array (static size) or string or ``bytes`` (dynamic size) to another contract?
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=====================================================================================================
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=====================================================================================================
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@ -465,11 +465,13 @@ a non-rational number).
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.. index:: literal, literal;string, string
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.. index:: literal, literal;string, string
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.. _string_literals:
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.. _string_literals:
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String Literals
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String Literals and Types
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---------------
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-------------------------
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String literals are written with either double or single-quotes (``"foo"`` or ``'bar'``). They do not imply trailing zeroes as in C; ``"foo"`` represents three bytes, not four. As with integer literals, their type can vary, but they are implicitly convertible to ``bytes1``, ..., ``bytes32``, if they fit, to ``bytes`` and to ``string``.
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String literals are written with either double or single-quotes (``"foo"`` or ``'bar'``). They do not imply trailing zeroes as in C; ``"foo"`` represents three bytes, not four. As with integer literals, their type can vary, but they are implicitly convertible to ``bytes1``, ..., ``bytes32``, if they fit, to ``bytes`` and to ``string``.
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For example, with ``bytes32 samevar = "stringliteral"`` the string literal is interpreted in its raw byte form when assigned to a ``bytes32`` type.
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String literals support the following escape characters:
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String literals support the following escape characters:
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- ``\<newline>`` (escapes an actual newline)
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- ``\<newline>`` (escapes an actual newline)
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@ -862,13 +864,20 @@ or create a new memory array and copy every element.
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}
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}
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}
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}
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.. index:: ! array;literals, !inline;arrays
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.. index:: ! array;literals, ! inline;arrays
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Array Literals / Inline Arrays
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Array Literals
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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^^^^^^^^^^^^^^
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Array literals are arrays that are written as an expression and are not
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An array literal is a comma-separated list of one or more expressions, enclosed
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assigned to a variable right away.
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in square brackets (``[...]``). For example ``[1, a, f(3)]``. There must be a
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common type all elements can be implicitly converted to. This is the elementary
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type of the array.
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Array literals are always statically-sized memory arrays.
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In the example below, the type of ``[1, 2, 3]`` is
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``uint8[3] memory``. Because the type of each of these constants is ``uint8``, if you want the result to be a ``uint[3] memory`` type, you need to convert the first element to ``uint``.
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::
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::
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@ -883,13 +892,7 @@ assigned to a variable right away.
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}
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}
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}
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}
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The type of an array literal is a memory array of fixed size whose base
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Fixed size memory arrays cannot be assigned to dynamically-sized memory arrays, i.e. the following is not possible:
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type is the common type of the given elements. The type of ``[1, 2, 3]`` is
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``uint8[3] memory``, because the type of each of these constants is ``uint8``.
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Because of that, it is necessary to convert the first element in the example
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above to ``uint``. Note that currently, fixed size memory arrays cannot
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be assigned to dynamically-sized memory arrays, i.e. the following is not
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possible:
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::
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::
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@ -904,8 +907,8 @@ possible:
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}
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}
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}
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}
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It is planned to remove this restriction in the future but currently creates
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It is planned to remove this restriction in the future, but it creates some
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some complications because of how arrays are passed in the ABI.
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complications because of how arrays are passed in the ABI.
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.. index:: ! array;length, length, push, pop, !array;push, !array;pop
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.. index:: ! array;length, length, push, pop, !array;push, !array;pop
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