IOS 数据库（FMDB）--- 源码介绍（FMDBResultSet）

概述

FMResultSet : 表示FMDatabase执行查询之后的结果集。

基本方法

初始化

+ (instancetype)resultSetWithStatement:(FMStatement *)statement usingParentDatabase:(FMDatabase*)aDB {
    
    FMResultSet *rs = [[FMResultSet alloc] init];
    
    [rs setStatement:statement];
    [rs setParentDB:aDB];
    
    NSParameterAssert(![statement inUse]);
    [statement setInUse:YES]; // weak reference
    
    return FMDBReturnAutoreleased(rs);
}

遍历

- (BOOL)nextWithError:(NSError **)outErr {
    
    int rc = sqlite3_step([_statement statement]);
    
    if (SQLITE_BUSY == rc || SQLITE_LOCKED == rc) {
        NSLog(@"%s:%d Database busy (%@)", __FUNCTION__, __LINE__, [_parentDB databasePath]);
        NSLog(@"Database busy");
        if (outErr) {
            *outErr = [_parentDB lastError];
        }
    }
    else if (SQLITE_DONE == rc || SQLITE_ROW == rc) {
        // all is well, let's return.
    }
    else if (SQLITE_ERROR == rc) {
        NSLog(@"Error calling sqlite3_step (%d: %s) rs", rc, sqlite3_errmsg([_parentDB sqliteHandle]));
        if (outErr) {
            *outErr = [_parentDB lastError];
        }
    }
    else if (SQLITE_MISUSE == rc) {
        // uh oh.
        NSLog(@"Error calling sqlite3_step (%d: %s) rs", rc, sqlite3_errmsg([_parentDB sqliteHandle]));
        if (outErr) {
            if (_parentDB) {
                *outErr = [_parentDB lastError];
            }
            else {
                // If 'next' or 'nextWithError' is called after the result set is closed,
                // we need to return the appropriate error.
                NSDictionary* errorMessage = [NSDictionary dictionaryWithObject:@"parentDB does not exist" forKey:NSLocalizedDescriptionKey];
                *outErr = [NSError errorWithDomain:@"FMDatabase" code:SQLITE_MISUSE userInfo:errorMessage];
            }
            
        }
    }
    else {
        // wtf?
        NSLog(@"Unknown error calling sqlite3_step (%d: %s) rs", rc, sqlite3_errmsg([_parentDB sqliteHandle]));
        if (outErr) {
            *outErr = [_parentDB lastError];
        }
    }
    
    
    if (rc != SQLITE_ROW) {
        [self close];
    }
    
    return

列名与该列的列数的一一对应关系

- (NSMutableDictionary *)columnNameToIndexMap {
    if (!_columnNameToIndexMap) {
        int columnCount = sqlite3_column_count([_statement statement]);
        _columnNameToIndexMap = [[NSMutableDictionary alloc] initWithCapacity:(NSUInteger)columnCount];
        int columnIdx = 0;
        for (columnIdx = 0; columnIdx < columnCount; columnIdx++) {
            [_columnNameToIndexMap setObject:[NSNumber numberWithInt:columnIdx]
                                      forKey:[[NSString stringWithUTF8String:sqlite3_column_name([_statement statement], columnIdx)] lowercaseString]];
        }
    }
    return _columnNameToIndexMap;
}

获取每一行中所有的结果集合

- (NSDictionary*)resultDictionary {
    
    NSUInteger num_cols = (NSUInteger)sqlite3_data_count([_statement statement]);
    
    if (num_cols > 0) {
        NSMutableDictionary *dict = [NSMutableDictionary dictionaryWithCapacity:num_cols];
        
        int columnCount = sqlite3_column_count([_statement statement]);
        
        int columnIdx = 0;
        for (columnIdx = 0; columnIdx < columnCount; columnIdx++) {
            
            NSString *columnName = [NSString stringWithUTF8String:sqlite3_column_name([_statement statement], columnIdx)];
            id objectValue = [self objectForColumnIndex:columnIdx];
            [dict setObject:objectValue forKey:columnName];
        }
        
        return dict;
    }
    else {
        NSLog(@"Warning: There seem to be no columns in this set.");
    }
    
    return nil;
}

kvc的支持

- (void)kvcMagic:(id)object {
    
    int columnCount = sqlite3_column_count([_statement statement]);
    
    int columnIdx = 0;
    for (columnIdx = 0; columnIdx < columnCount; columnIdx++) {
        
        const char *c = (const char *)sqlite3_column_text([_statement statement], columnIdx);
        
        // check for a null row
        if (c) {
            NSString *s = [NSString stringWithUTF8String:c];
            
            [object setValue:s forKey:[NSString stringWithUTF8String:sqlite3_column_name([_statement statement], columnIdx)]];
        }
    }
}