SecItemCopyMatching 是对此的正确调用。首先，我们构建查询字典，以便在字典中返回项目的属性，并返回所有项目：

SecItemCopyMatching is the right call for that. First we build our query dictionary so that the items' attributes are returned in dictionaries, and that all items are returned:

NSMutableDictionary *query = [NSMutableDictionary dictionaryWithObjectsAndKeys:
    (__bridge id)kCFBooleanTrue, (__bridge id)kSecReturnAttributes,
    (__bridge id)kSecMatchLimitAll, (__bridge id)kSecMatchLimit,
    nil];

As SecItemCopyMatching 至少要求返回的 SecItem s，我们创建一个包含所有类的数组...

As SecItemCopyMatching requires at least the class of the returned SecItems, we create an array with all the classes…

NSArray *secItemClasses = [NSArray arrayWithObjects:
                           (__bridge id)kSecClassGenericPassword,
                           (__bridge id)kSecClassInternetPassword,
                           (__bridge id)kSecClassCertificate,
                           (__bridge id)kSecClassKey,
                           (__bridge id)kSecClassIdentity,
                           nil];

...并且对于每个类，在我们的查询中设置类，调用 SecItemCopyMatching ，并记录结果。

…and for each class, set the class in our query, call SecItemCopyMatching, and log the result.

for (id secItemClass in secItemClasses) {
    [query setObject:secItemClass forKey:(__bridge id)kSecClass];

    CFTypeRef result = NULL;
    SecItemCopyMatching((__bridge CFDictionaryRef)query, &result);
    NSLog(@"%@", (__bridge id)result);
    if (result != NULL) CFRelease(result);
}

在生产代码中，您应该检查 OSStatus 返回的 SecItemCopyMatching 是 errSecItemNotFound （未找到任何项目）或 errSecSuccess （至少找到一个项目）。

In production code, you should check that the OSStatus returned by SecItemCopyMatching is either errSecItemNotFound (no items found) or errSecSuccess (at least one item was found).