Use MusicBrainz in iOS（三）查询专辑的完整信息

本文讨论下通过专辑名获取专辑的完整信息，包括歌曲列表，艺术家列表，发行时间和地区等。

由于是通过专辑名搜索专辑信息，所以搜索出来的结果可能较多，例如一个“Violin Concertos”就可能包含多个搜索结果，而本文只是显示专辑的完整信息，并不进行进一步的匹配工作，因此以第一个搜索结果为例。

代码如下：

#import "AlbumViewController.h"#import "MB.h"#import "ResultViewController.h"#define UnknownString @"未知"#define UnknownInteger 0@interface AlbumViewController ()@property (strong, nonatomic) ResultViewController *resultController;@property (copy, nonatomic) RequestFailureBlock failureBlock;@end@implementation AlbumViewController@synthesize resultController = _resultController;- (void)viewDidLoad{    [super viewDidLoad];        self.resultController = [[UIStoryboard storyboardWithName:@"Main" bundle:nil] instantiateViewControllerWithIdentifier:@"ResultViewController"];        self.failureBlock = ^(MBRequest *request, NSError *error, NSData *data) {        NSString *message = [NSString stringWithFormat:@"错误：%@", [error localizedDescription]];        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"警告"                                                            message:message                                                           delegate:nil                                                  cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];        [alertView show];    };}- (void)alertWithMessage:(NSString *)message {    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"警告" message:message delegate:nil cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];    [alertView show];}- (IBAction)search:(id)sender {    MBConnection *conn = [MBConnection connection];        RequestSuccessBlock successBlock = ^(MBRequest *request, MBMetadata *metadata) {        MBList    *list    = metadata.ReleaseList;        MBRelease *release = [list elementAtIndex:0];                // 专辑的mbid        _resultController.mbid = (release.Id) ? release.Id : UnknownString;        if (!release.Id) {            [self alertWithMessage:@"搜索失败"];            return;        }                // 专辑名        _resultController.title = (release.Title) ? release.Title : UnknownString;                // 专辑状态        _resultController.status = (release.Status) ? release.Status : UnknownString;                // 专辑音质        _resultController.quality = (release.Quality) ? release.Quality : UnknownString;                MBTextRepresentation *textRepresentation = release.TextRepresentation;                // 专辑语言        _resultController.language = (textRepresentation.Language) ? textRepresentation.Language : UnknownString;                // 专辑剧本语言        _resultController.script = (textRepresentation.Script) ? textRepresentation.Script : UnknownString;                MBArtistCredit *artistCredit = release.ArtistCredit;        NSUInteger nameCount = (artistCredit.elementCount) ? artistCredit.elementCount : UnknownInteger;                // 专辑艺术家列表        _resultController.artists = [NSMutableArray array];        for (int i = 0; i < nameCount; i++) {            MBNameCredit *nameCredit = [artistCredit elementAtIndex:i];            [_resultController.artists addObject:nameCredit.Artist.Name];        }                MBReleaseGroup *group = release.ReleaseGroup;        NSLog(@"发行组织类型 = %@", group.Type);        NSLog(@"发行组织名称 = %@", group.Title);                // 专辑发行日期        _resultController.date = (release.Date) ? release.Date : UnknownString;                // 专辑发行国家        _resultController.country = (release.Country) ? release.Country : UnknownString;                NSLog(@"专辑条形码 = %@", release.Barcode);        NSLog(@"Asin 标准识别码，来自卓越亚马逊 = %@", release.Asin);                MBList *mediumList = release.MediumList;        MBMedium *medium = [mediumList elementAtIndex:1];                // 专辑发行形式        _resultController.format = medium.Format;                NSLog(@"专辑中的音乐个数 = %d", medium.TrackList.Count.integerValue);                // 用一个列表显示出专辑的详细信息        [self showAllData:release.Id];    };        MBRequest *req = [MBRequest searchForEntity:MBEntityRelease                                          query:@"Violin Concertos"//                                          query:@"不想放手"                                          limit:[NSNumber numberWithInteger:10]                                         offset:[NSNumber numberWithInteger:0]];        [conn enqueueRequest:req onSuccess:successBlock onFailure:self.failureBlock];}- (void)showAllData:(NSString *)mbid {    MBConnection *conn = [MBConnection connection];        MBRequest *req = [MBRequest lookupWithEntity:MBEntityRelease                                            mbid:mbid                                   incParameters:(MBIncParameterRecordings | MBIncParameterRecordingRels)];        void (^successBlock)(MBRequest *, MBMetadata *) = ^(MBRequest *request, MBMetadata *metadata) {        MBRelease *release = metadata.Release;        if (release) {            _resultController.tracks = [NSMutableArray array];            MBList *mediumList = release.MediumList;            MBMedium *medium = [mediumList elementAtIndex:0];            MBList *trackList = medium.TrackList;            for (MBTrack *track in trackList) {                [_resultController.tracks addObject:track.Recording.Title];            }            [self.navigationController pushViewController:_resultController animated:YES];            NSLog(@"Success");        }        else {            [self alertWithMessage:@"搜索失败"];        }    };        [conn enqueueRequest:req onSuccess:successBlock onFailure:self.failureBlock];}@end

事实上，这和Use MusicBrainz in iOS（二）中的搜索方法是一样的，只是搜索的类型是MBEntityRelease。在搜索并获取到列表中的第一个结果后，我们选取其mbid进行进一步的查询，因为只有通过mbid的查询才能查找到该专辑中包含什么歌曲等信息。

在查询成功后，用一个表格来加载这些数据。ResultViewController类代码如下：

#import <UIKit/UIKit.h>@interface ResultViewController : UITableViewController@property (strong, nonatomic) NSMutableArray *tracks;@property (strong, nonatomic) NSMutableArray *artists;@property (copy, nonatomic) NSString *title;@property (copy, nonatomic) NSString *mbid;@property (copy, nonatomic) NSString *date;@property (copy, nonatomic) NSString *country;@property (copy, nonatomic) NSString *format;@property (copy, nonatomic) NSString *language;@property (copy, nonatomic) NSString *script;@property (copy, nonatomic) NSString *quality;@property (copy, nonatomic) NSString *status;@end

#import "ResultViewController.h"@interface ResultViewController ()@end@implementation ResultViewController- (void)viewDidLoad {    [super viewDidLoad];}- (void)viewWillAppear:(BOOL)animated {    [super viewWillAppear:animated];        self.navigationItem.title = self.title;}#pragma mark - Table view data source- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView {    return 4;}- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section {    switch (section) {        case 0:            return [self.tracks count];        case 1:            return [self.artists count];        case 2:            return 5;        case 3:            return 2;        default:            return 0;    }}- (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInteger)section {    switch (section) {        case 0:            return @"音乐列表";        case 1:            return @"艺术家";        case 2:            return @"基本信息";        case 3:            return @"附加信息";        default:            return @"";    }}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:@"CellIdentifier" forIndexPath:indexPath];        if (indexPath.section == 0) {        cell.textLabel.text = self.tracks[indexPath.row];    }    else if (indexPath.section == 1) {        cell.textLabel.text = self.artists[indexPath.row];    }    else if (indexPath.section == 2) {        NSString *text;        switch (indexPath.row) {            case 0:                text = [NSString stringWithFormat:@"发行日期：%@", self.date];                break;            case 1:                text = [NSString stringWithFormat:@"发行地区：%@", self.country];                break;            case 2:                text = [NSString stringWithFormat:@"发行形式：%@", self.format];                break;            case 3:                text = [NSString stringWithFormat:@"语言：%@", self.language];                break;            case 4:                text = [NSString stringWithFormat:@"Script：%@", self.script];                break;            default:                break;        }        cell.textLabel.text = text;    }    else if (indexPath.section == 3) {        NSString *text;        switch (indexPath.row) {            case 0:                text = [NSString stringWithFormat:@"品质：%@", self.quality];                break;            case 1:                text = [NSString stringWithFormat:@"状态：%@", self.status];                break;            default:                break;        }        cell.textLabel.text = text;    }        return cell;}@end

运行结果如下：

程序可能会继续修改，看看明天有什么进一步的需求提出来吧。