Swift簡易使用(配列)

最近swiftを固めて、いくつかの基礎の用法を総括して、必要な人を助けたいです

 //MARK: -     
    func demo2(){
        let array = ["zhang","wang","li","zhao"]
        
        //1.      
        for i in 0..  ,c->   ,n c        
        for(n,c)in array.enumerate(){
            print("\(n)\(c)")
        }
        
        //5.      
        for s in array.reverse(){
            print(s)
        }
        
        //6.      
        for s in array.reverse().enumerate(){
            print(s)//(0, "zhao"),       ,   
            
            print("----")
            print("\(s.index)")//  
            print("\(s.element)")//  
        
        }

    }

//MARK: -     
    func demo5(){
        var arr1 = [12,22,33,55]
        let arr2 = [00,233,99,22]
        
        // arr2    arr1,           ,       
        arr1 += arr2
        print(arr1)
    }
    
    //MARK: -       
    func demo4(){
        //    ,     ,      
        var array :[String]
        //          
        array = [String]()
//
        //      ,       
        var array2 = [Int]()
        print(array2.capacity)//  
        
        //    ,       
        //    ,         ,          *2
        for i in 0..<9{
            array2.append(i)
            print("\(array2) -- \(array2.capacity)" )
        }
        
    }
    
    //MARK: -            var     let
    func demo3(){
        var array = ["zhang","li","wei"]
        
//        var array = [1,2,3];
        //  ,                   
        array.append("xiaohua")
        print(array)
        
        //  
        array[0] = "laowang"
        print(array)
        
        //  
        array.removeAll()
        print(array)//    ,     
      
}