Question

我正在尝试在Xcode中创建一个新的Objective-C类，并且在.m文件中遇到了上述几个错误。

#import "Query.h"

@implementation Query {

MPMediaQuery *query = [[MPMediaQuery alloc] init]; //create new query



[[query addFilterPredicate: [MPMediaPropertyPredicate
                            predicateWithValue: @"Vampire Weekend"
                            forProperty: MPMediaItemPropertyArtist]]; //filter out artists except for Vampire Weekend
// Sets the grouping type for the media query
[query setGroupingType: MPMediaGroupingAlbum]; //sort by album

NSArray *albums = [query collections];
for (MPMediaItemCollection *album in albums) {
    MPMediaItem *representativeItem = [album representativeItem];
    NSString *artistName =
    [representativeItem valueForProperty: MPMediaItemPropertyArtist];
    NSString *albumName =
    [representativeItem valueForProperty: MPMediaItemPropertyAlbumTitle];
    NSLog (@"%@ by %@", albumName, artistName);

    NSArray *songs = [album items];
    for (MPMediaItem *song in songs) {
        NSString *playCount = [song valueForProperty:MPMediaItemPropertyPlayCount];
        NSString *lastPlayed = [song valueForProperty:MPMediaItemPropertyLastPlayedDate];
        NSString *songTitle =
        [song valueForProperty: MPMediaItemPropertyTitle];

        //NSString *info = [[NSString alloc] initWithFormat: @"%@ has been played %@ times.\n Last played %@.", songTitle, playCount, lastPlayed];
        NSLog(@"\n%@ has been played %@ times.\n Last played %@.", songTitle, playCount, lastPlayed);

    }
}
// Override point for customization after application launch.
[query release];

}

@end

Xcode吓坏了，并在我定义一个对象的行上给出错误，或者尝试使用查询（因为它是未定义的）。

我的头文件如下（不完整，但我停下来处理这个）：

#import <Foundation/Foundation.h>
#import <MediaPlayer/MediaPlayer.h>

@interface Query : NSObject {
  MPMediaQuery *query;
}

@property (nonatomic, retain) MPMediaQuery *query;

@end

Answer 1

您需要将代码放在方法中 - 您不能在实现中“松散”。

Answer 2

@implementation之后你不需要花括号，你需要将代码放在某个方法中！

它应该是这样的：

@implementation Query

- (void)aMethod {
    // Code here
}

@end

预期';'在声明结束列表

2 个答案: