Realization of variable length parameter in objective-c

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OBJC does not provide a direct variable-length parameter method, which requires the use of the Av_list method in the C standard library, and is simply used as follows:

2. -(void) Somethingforyou: (NSString *) vstring,.... {
4. Va_list varlist;
6. ID arg;
8. Nsmutablearray *Argsarray = [[Nsmutablearray alloc]inti];
10. if (vstring) {
12. Va_start (varlist,vstring);
14. while (arg = va_arg (varlist,id)) {
16. [Argsarray Addobject:arg];
18. }
20. Va_end (varlist);
22. }
24. }

C Language Library files

Va_list argList: Defines a pointer to a variable number of parameter lists;
Va_start (arglist,statement): Causes the argument list pointer arg_ptr to point to the first optional parameter in the function argument list, stating: Argn is a fixed parameter before the first optional parameter, (or, last fixed argument; ...). Previous parameter), the order of the parameters in the function argument list in memory is consistent with the order in which the function is declared. If there is a declaration of a VA function that is void va_test (char A, char B, char C, ...), then its fixed parameters are a,b,c, the last fixed argument argn C, and therefore Va_start (Arg_ptr, C).

Va_arg (Arglist,id): Returns the parameter in the argument list that is referred to by the pointer arg_ptr, returns the type to, and causes the pointer arg_ptr to point to the next parameter in the parameter list.
Va_end (ARG_PTR): Clears the argument list and invalidates the parameter pointer arg_ptr.

Typical applications:

Add nil at the end of the argument at the time of the call

SqlHelper *sqlcom = [[SqlHelper alloc] init];
[Sqlcom somethingforyou:@ "INSERT into Authorinfo (author,age) VALUES (?,?)" @ "cheungching" @ "+", nil];

Realization of variable length parameter in objective-c