这似乎是一件容易的事，至少在VB.net中是这样。我只需要根据传递给方法的字符串引用数组。当视图控制器加载时，调用方法并传递字符串。将基于此字符串创建URL，并将从中获取JSON。我想要的是方法根据传递的字符串填充适当的数组。
这里我们看到方法“goGetData”在类“getData”中被调用，其中包含三个字符串参数之一“workshop / speaker / exhibitor”：
- (void)viewDidLoad
{
[getData goGetData:@"workshop"];
[getData goGetData:@"speaker"];
[getData goGetData:@"exhibitor"];
getData *getDataInstance = [[getData alloc] init];
NSArray *newTablesArray = getDataInstance.jsonAllTables;
NSLog(@"Json currently = %@", newTablesArray);
[super viewDidLoad];
[[self myTableView]setDelegate:self];
[[self myTableView]setDataSource:self];
arrayTable =[[NSMutableArray alloc]init];
}
例如，如果用“speaker”触发“goGetDate”，我需要获取扬声器数据，然后填充“_jsonSpeaker”数组。到目前为止，我尝试根据方法调用中传递的字符串来引用和填充数组：
#import "getData.h"
@implementation getData
+(void)goGetData:(NSString *)requestedTable
{
getData *getDataInstance = [[getData alloc] init];
[getDataInstance buildArray];
[getDataInstance fetchData:requestedTable];
}
-(void)buildArray{
// I tried putting the arrays in an array but still do no know how to reference them
_jsonAllTables = [[NSMutableArray alloc] initWithObjects:_jsonExhibitor, _jsonSpeaker, _jsonWorkshop, nil];
}
-(void)fetchData:(NSString *)requestedTable{
NSString *varCurrentTable;
varCurrentTable = [NSString stringWithFormat:@"_json%@", requestedTable];
NSString *requestedURL;
requestedURL = [NSString stringWithFormat:@"http://testapi.website.com/api/%@", requestedTable];
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:requestedURL]];
[NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if (response){
NSHTTPURLResponse *newResp = (NSHTTPURLResponse*)response;
if (newResp.statusCode == 200) {
// STUFF FOR TESTING NSLog(@"Response to request: %@ is: %i GOOD", requestedURL, newResp.statusCode);
if ([data length] >0 && error == nil)
{
// STUFF FOR TESTING NSUInteger indexOfArray = [_jsonAllTables indexOfObject:varCurrentTable];
// STUFF FOR TESTING NSString *objectAtIndexOfArray = [_jsonAllTables objectAtIndex:indexOfArray];
// This is the part I think I am stuck on:
// "CURRENT TABLE TO BE POPULATED" = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];
}
else if ([data length] == 0 && error == nil)
{
NSLog(@"Nothing was downloaded");
}
else if (error != nil)
{
NSLog(@"Error: %@", error);
}
} else if (newResp.statusCode == 404){
NSLog(@"Response to request: %@ is: %i BAD - URL incorrect", requestedURL, newResp.statusCode);
} else {
// add more returned status error handling here
}
}else{
NSLog(@"No response received");
}
}];
}
@end
谢谢，
为了澄清我想要达到的目的而添加：为了节省大量的一遍又一遍地写出同样的东西，可能是Obj-c中的以下内容（请原谅语言的混搭）
NSArray *ListOfTables = [NSArray arrayWithObjects:@"Speaker", @"Exhibitor", @"Workshop", nil];
For i as int = 0 to ListOfTables.count{
[self fetchData:(ListOfTables.objectAtIndex = i) withCompletion:^(NSArray* objects, NSError*error){
dispatch_async(dispatch_get_main_queue(), ^{
if (objects) {
self.(ListOfTables.objectAtIndex = i) = objects;
}
else {
NSLog(@"Error: %error", error);
}
});
}];
i++;
Next
};
注意我没有为每个表调用单独的方法，而是每次调用相同的方法但使用不同的表名参数。我似乎无法在Xcode中找到这样的占位符的实例。
答案 0 :(得分：1)
您可能想要一个异步的方法，并通过完成处理程序返回结果：
typedef void(^completion_t)(NSArray* objects, NSError*error);
-(void)fetchData:(NSString *)tableName
withCompletion:(completion_t)completionHandler;
- (void) foo {
[self fetchData:tableName1 withCompletion:^(NSArray* objects, NSError*error){
dispatch_async(dispatch_get_main_queue(), ^{
if (objects) {
self.table1 = objects;
}
else {
NSLog(@"Error: %error", error);
}
});
}];
[self fetchData:tableName2 withCompletion:^(NSArray* objects, NSError*error){
dispatch_async(dispatch_get_main_queue(), ^{
if (objects) {
self.table2 = objects;
}
else {
NSLog(@"Error: %error", error);
}
});
}];
[self fetchData:tableName3 withCompletion:^(NSArray* objects, NSError*error){
dispatch_async(dispatch_get_main_queue(), ^{
if (objects) {
self.table3 = objects;
}
else {
NSLog(@"Error: %error", error);
}
});
}];
}
typedef void(^completion_t)(NSArray* objects, NSError* error);
-(void)fetchData:(NSString *)tableName
withCompletion:(completion_t)completionHandler
{
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:tableName]];
// Setup HTTP headers, e.g. "Accept: application/json", etc.
...
[NSURLConnection sendAsynchronousRequest:request
queue:[[NSOperationQueue alloc] init]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
NSError* err = error;
NSArray* objects; // final result array as a representation of JSON Array
if (response) {
NSHTTPURLResponse *newResp = (NSHTTPURLResponse*)response;
if (newResp.statusCode == 200) {
if ([data length] >0 && error == nil)
{
NSError* localError;
objects = ... // Use NSJSONSerialization to obtain a representation
if (objects) {
if (completionHandler) {
completionHandler(object, nil);
}
return;
}
else {
err = localError;
}
}
else {
err = ...
}
}
}
if (objects == nil) {
assert(err);
if (completionHandler) {
completionHandler(nil, err);
}
}
}];
}
另一个例子，用于加载一堆数据：
首先，实现了一个“异步循环”的方法：
typedef void(^completion_t)(id result, NSError* error);
- (void) fetchObjectsWithTableNames:(NSMutableArray*)tableNames
completion:(completion_t)completionHandler;
此方法本身是异步的，因此是完成处理程序。
- (void) foo
{
NSArray* tableNames = @[@"A", @"B", @"C"]; // possibly 1000
[self fetchObjectsWithTableNames:[tableNames mutableCopy]:^(id result, NSError*error){
if (error) {
NSLog(@"Error: %@", error);
}
else {
// finished fetching a bunch of datas with result:
NSLog(@"Result: %@", result);
}
}];
}
- (void) fetchObjectsWithTableNames:(NSMutableArray*)tableNames
completion:(completion_t)completionHandler;
{
if ([tableNames count] > 0) {
NSString* name = [tableNames firstObject];
[tableNames removeObjectAtIndex:0];
[self fetchData:name withCompletion:^(NSArray* objects, NSError*error){
if (objects) {
[self.tables addObject:objects];
[self fetchObjectsWithTableNames:tableNames completion:completionHandler];
}
else {
// handle error
}
}];
}
else {
// finished
if (completionHandler) {
completionHandler(@"finished", nil);
}
}
}