How to use Uisearchbar controls in IOS to limit the number of input words _ios

Nonsense not to say, directly to everyone on the key code, the specific code as described below:

-(void) Searchbar: (Uisearchbar *) Searchbar textdidchange: (NSString *) SearchText//called when text changes (including CL Ear)
{
if (SearchBar.text.length > Imput_max) {
searchbar.text = [Searchbar.text substringtoindex:15];
}
}

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