lua - Lua，表的大小（#table_name 或 table.getn(table_name)，它有时返回 0

Question

什么#table_name时候返回非 0 值？再说一次，什么table.getn(table_name)时候返回非 0 值？

Answer 1

Go through the manual:

2.5.5 - The Length Operator

The length operator is denoted by the unary operator #. The length of a string is its number of bytes (that is, the usual meaning of string length when each character is one byte).

The length of a table t is defined to be any integer index n such that t[n] is not nil and t[n+1] is nil; moreover, if t[1] is nil, n can be zero. For a regular array, with non-nil values from 1 to a given n, its length is exactly that n, the index of its last value. If the array has "holes" (that is, nil values between other non-nil values), then #t can be any of the indices that directly precedes a nil value (that is, it may consider any such nil value as the end of the array).

Answer 2

如果表中的键不是整数（例如字符串），则长度运算符将返回 0。