# Method `->=()

Method `->=

  `mixed `->=(object arg, string index, mixed val)`
  `mixed `->=(mapping arg, string index, mixed val)`
  `bool `->=(multiset arg, string index, bool val)`

Description

  Arrow index assignment.

  Every lvalue expression with the `->` operator becomes a call to this function, i.e. `a->b=c` is the same as `predef::`->=(a,"b",c)` where `"b"` is the symbol `b` in string form.

  This function behaves like `[]=, except that the index is passed literally as a string instead of being evaluated.

  If arg is an object that implements lfun::`->=(), that function will be called with index and val as the arguments.

  `arg` can have any of the following types:

  `object` | The non-protected (ie public) variable named index will be looked up in arg, and assigned val.
  `array|mapping` | Index index in arg will be assigned val.
  `multiset` | If val is `0` (zero), one occurrance of index in arg will be removed. Otherwise index will be added to arg if it is not already there.

Returns

  val will be returned.

Note

  In an expression `a->b=c`, the symbol `b` can be any token that matches the identifier syntax - keywords are disregarded in that context.

Note

  An arrow indexing expression in a non-lvalue context, i.e. where the index is being queried instead of assigned, uses `-> instead of this function.

See also

  `[]=(), lfun::`->=(), `->