如何删除NSDictionary或NSArray中的NSNull

前段时间与某公司的技术交流，被问到一个问题，如何删除NSDictionary中的NSNull。当时在纸上写，以前太依赖Xcode编译器了，以至于方法名都写不全，最终也没写出来，我想我肯定被鄙视的体无完肤。

最近有机会实现了一下。先来递归实现方案：

// 删除NSArray中的NSNull
- (NSMutableArray *)removeNullFromArray:(NSArray *)arr
{
    NSMutableArray *marr = [NSMutableArray array];
    for (int i = 0; i < arr.count; i++) {
        NSValue *value = arr[i];
        // 删除NSDictionary中的NSNull，再添加进数组
        if ([value isKindOfClass:NSDictionary.class]) {
            [marr addObject:[self removeNullFromDictionary:(NSDictionary *)value]];
        }
        // 删除NSArray中的NSNull，再添加进数组
        else if ([value isKindOfClass:NSArray.class]) {
            [marr addObject:[self removeNullFromArray:(NSArray *)value]];
        }
        // 剩余的非NSNull类型的数据添加进数组
        else if (![value isKindOfClass:NSNull.class]) {
            [marr addObject:value];
        }
    }
    return marr;
}
// 删除Dictionary中的NSNull
- (NSMutableDictionary *)removeNullFromDictionary:(NSDictionary *)dic
{
    NSMutableDictionary *mdic = [NSMutableDictionary dictionary];
    for (NSString *strKey in dic.allKeys) {
        NSValue *value = dic[strKey];
        // 删除NSDictionary中的NSNull，再保存进字典
        if ([value isKindOfClass:NSDictionary.class]) {
            mdic[strKey] = [self removeNullFromDictionary:(NSDictionary *)value];
        }
        // 删除NSArray中的NSNull，再保存进字典
        else if ([value isKindOfClass:NSArray.class]) {
            mdic[strKey] = [self removeNullFromArray:(NSArray *)value];
        }
        // 剩余的非NSNull类型的数据保存进字典
        else if (![value isKindOfClass:NSNull.class]) {
            mdic[strKey] = dic[strKey];
        }
    }
    return mdic;
}

很美观哈。俩方法，第一个方法能将NSArray中的NSNull删除，第二方法能将NSDictionary中的NSNull删除。



        可是，可是，我更喜欢非递归算法的呀，尤其在AI搜索里。用递归的话，很担心考虑不周全导致少计算一大块。下面，就来一发非递归的方案。代码如下：

- (NSObject *)removeNullFrom:(NSObject *)object
{
    NSObject *objResult = nil;
    NSMutableArray *marrSearch = nil;
    if ([object isKindOfClass:NSNull.class]) {
        return nil;
    }
    else if ([object isKindOfClass:NSArray.class]) {
        objResult = [NSMutableArray arrayWithArray:(NSArray *)object];
        marrSearch = [NSMutableArray arrayWithObject:objResult];
    }
    else if ([object isKindOfClass:NSDictionary.class]) {
        objResult = [NSMutableDictionary dictionaryWithDictionary:(NSDictionary *)object];
        marrSearch = [NSMutableArray arrayWithObject:objResult];
    }
    else {
        return object;
    }
    while (marrSearch.count > 0) {
        NSObject *header = marrSearch[0];
        if ([header isKindOfClass:NSMutableDictionary.class]) {
            // 遍历这个字典
            NSMutableDictionary *mdicTemp = (NSMutableDictionary *)header;
            for (NSString *strKey in mdicTemp.allKeys) {
                NSObject *objTemp = mdicTemp[strKey];
                // 将NSDictionary替换为NSMutableDictionary
                if ([objTemp isKindOfClass:NSDictionary.class]) {
                    NSMutableDictionary *mdic = [NSMutableDictionary dictionaryWithDictionary:(NSDictionary *)objTemp];
                    mdicTemp[strKey] = mdic;
                    [marrSearch addObject:mdic];
                }
                // 将NSArray替换为NSMutableArray
                else if ([objTemp isKindOfClass:NSArray.class]) {
                    NSMutableArray *marr = [NSMutableArray arrayWithArray:(NSArray *)objTemp];
                    mdicTemp[strKey] = marr;
                    [marrSearch addObject:marr];
                }
                // 删除NSNull
                else if ([objTemp isKindOfClass:NSNull.class]) {
                    mdicTemp[strKey] = nil;
                }
            }
        }
        else if ([header isKindOfClass:NSMutableArray.class]) {
            // 遍历这个数组
            NSMutableArray *marrTemp = (NSMutableArray *)header;
            for (int i = marrTemp.count-1; i >= 0; i--) {
                NSObject *objTemp = marrTemp[i];
                // 将NSDictionary替换为NSMutableDictionary
                if ([objTemp isKindOfClass:NSDictionary.class]) {
                    NSMutableDictionary *mdic = [NSMutableDictionary dictionaryWithDictionary:(NSDictionary *)objTemp];
                    [marrTemp replaceObjectAtIndex:i withObject:mdic];
                    [marrSearch addObject:mdic];
                }
                // 将NSArray替换为NSMutableArray
                else if ([objTemp isKindOfClass:NSArray.class]) {
                    NSMutableArray *marr = [NSMutableArray arrayWithArray:(NSArray *)objTemp];
                    [marrTemp replaceObjectAtIndex:i withObject:marr];
                    [marrSearch addObject:marr];
                }
                // 删除NSNull
                else if ([objTemp isKindOfClass:NSNull.class]) {
                    [marrTemp removeObjectAtIndex:i];
                }
            }
        }
        else {
            // 到这里就出错了
        }
        [marrSearch removeObjectAtIndex:0];
    }
    return objResult;
}

一个方法，所有类型全搞定。

发帖地址：http://www.cocoachina.com/bbs/read.php?tid=331661