OC 自带方法 简绍 3 NSArray

1.initWithObjects   //

例子      

NSArray * array = [[NSArray alloc] initWithObjects:@"A", @"B",@"C" ,@"D" ,@"E" , nil];

NSLog(@"%@", array);

        //arrayWithObjects  是initWithObjects 的便利构造器
        NSArray * array = [NSArray arrayWithObjects:@"11", @"22", @"33", nil];
        NSLog(@"%@", array);

2. //objectAtIndex //根据下标 得到数组中某个元素

- (id)objectAtIndex:(NSUInteger)index   //  Returns the object at the specified index of the set.

例子

        NSString * str = [array objectAtIndex:1];
        NSLog(@"%@", str);

3. firstObject //@property(nonatomic, readonly) id firstObject  . // 得到数组中第一个值

    lastObject // @property(nonatomic, readonly) id lastObject  .// 得到数组中最后一个值

例子

        NSLog(@"%@", [array firstObject]);// 得到数组第一个元素
        NSLog(@"%@", [array lastObject]);// 得到数组最后一个元素

4.containsObject   //判断 某个字符串在数组中是否存在

virtual bool containsObject( const OSMetaClassBase *anObject) const; //Checks the set for the presence of an object.

例子

        BOOL b = [array containsObject:p];
        NSLog(@"%@", b ? @"YES" : @"NO");

5.indexOfObject  //得到数组中某个元素的下标

- (NSUInteger)indexOfObject:(id)anObject  // Returns the lowest index whose corresponding array value is equal to a given object.

例子

        Person * p = [[Person alloc] initWithName:@"fu" sex:@"nan" age:30];
        Person * p1 = [[Person alloc] initWithName:@"lu" sex:@"nan" age:30];
        Person * p2 = [[Person alloc] initWithName:@"shou" sex:@"nan" age:30];
        NSArray * array = [NSArray arrayWithObjects:p, p1, p2, nil];
        NSUInteger n1 = [array indexOfObject:p1];
        NSLog(@"%lu", n1);

6.isEqualToArray   判断两个数组是否相等

- (BOOL)isEqualToArray:(NSArray *)otherArray //Compares the receiving array to another array.

        BOOL bb = [array isEqualToArray:array];
        NSLog(@"%@", bb ? @"YES" : @"NO");