The carbocation electrophile in a friedel-crafts reaction can be generated in ways other than by reaction of an alkyl chloride with alcl3.give an example

iron (II) Chloride can be used instead of AlCl3

Explanation:

Friedel–Crafts alkylation reaction involves the introduction of alkyl group in  an aromatic ring with an alkyl halide using a strong Lewis acid, such as aluminium chloride, ferric chloride, or other MXn reagent, as catalyst.

The function of AlCl3 or fecl3 in Friedel-Craft reaction, is to produce electrophile, which later adds to benzene ring. This electrophilic aromatic substitution allows the synthesis of monoacylated products from the reaction between arenes and acyl chlorides or anhydrides. The products are deactivated and do not undergo a second substitution. Normally, a stoichiometric amount of the Lewis acid catalyst is required for both the substrate and the product form complexes.

AlCl3 or fecl3 (and other Lewis acids like it) will coordinate to halogens, and facilitate the breaking of these bonds. In doing so, it increases the electrophilic nature of its binding partner, making it much more reactive as to complete the reaction.

it is the most commonly accepted one