Require ResultSet to just implement `read`, optionally implementing `read(T.class)`. Fixes #5

spec/custom_drivers_types_spec.cr

@@ -16,18 +16,7 @@ module GenericResultSet
     index.to_s
   end
 
-  def column_type(index : Int32)
-    @row[index].class
-  end
-
-  {% for t in DB::TYPES %}
-    # Reads the next column as a nillable {{t}}.
-    def read?(t : {{t}}.class) : {{t}}?
-      read_and_move_next_column as {{t}}?
-    end
-  {% end %}
-
-  def read_and_move_next_column
+  def read
     @index += 1
     @row[@index - 1]
   end
@@ -89,10 +78,6 @@ class FooDriver < DB::Driver
     def initialize(statement, @row : Array(FooDriver::Any))
       super(statement)
     end
-
-    def read?(t : FooValue.class) : FooValue?
-      read_and_move_next_column.as(FooValue?)
-    end
   end
 end
 
@@ -152,10 +137,6 @@ class BarDriver < DB::Driver
     def initialize(statement, @row : Array(BarDriver::Any))
       super(statement)
     end
-
-    def read?(t : BarValue.class) : BarValue?
-      read_and_move_next_column.as(BarValue?)
-    end
   end
 end
 
@@ -174,8 +155,8 @@ describe DB do
         db.query "query" do |rs|
           w.check
           rs.move_next
-          rs.read?(Int32).should eq(1)
-          rs.read?(String).should eq("string")
+          rs.read(Int32).should eq(1)
+          rs.read(String).should eq("string")
           rs.read(FooValue).value.should eq(3)
         end
       end
@@ -188,8 +169,8 @@ describe DB do
           w.check
           rs.move_next
           rs.read(BarValue).value.should eq(4)
-          rs.read?(String).should eq("lorem")
-          rs.read?(Float64).should eq(1.0)
+          rs.read(String).should eq("lorem")
+          rs.read(Float64).should eq(1.0)
         end
       end
     end
@@ -208,7 +189,7 @@ describe DB do
         FooDriver.fake_row = [1] of FooDriver::Any
         db.query "query" do |rs|
           rs.move_next
-          expect_raises Exception, "read?(t : BarValue) is not implemented in FooDriver::FooResultSet" do
+          expect_raises(TypeCastError) do
             w.check
             rs.read(BarValue)
           end
@@ -221,7 +202,7 @@ describe DB do
         BarDriver.fake_row = [1] of BarDriver::Any
         db.query "query" do |rs|
           rs.move_next
-          expect_raises Exception, "read?(t : FooValue) is not implemented in BarDriver::BarResultSet" do
+          expect_raises(TypeCastError) do
             w.check
             rs.read(FooValue)
           end

spec/dummy_driver.cr

@@ -73,12 +73,10 @@ class DummyDriver < DB::Driver
   end
 
   class DummyResultSet < DB::ResultSet
-    @@next_column_type = String
     @top_values : Array(Array(String))
     @values : Array(String)?
 
     @@last_result_set : self?
-    @@next_column_type : Nil.class | String.class | Int32.class | Int64.class | Float32.class | Float64.class | Bytes.class
 
     def initialize(statement, query)
       super(statement)
@@ -108,15 +106,7 @@ class DummyDriver < DB::Driver
       "c#{index}"
     end
 
-    def column_type(index : Int32)
-      @@next_column_type
-    end
-
-    def self.next_column_type=(value)
-      @@next_column_type = value
-    end
-
-    private def read? : DB::Any?
+    def read
       n = @values.not_nil!.shift?
       raise "end of row" if n.is_a?(Nil)
       return nil if n == "NULL"
@@ -128,38 +118,36 @@ class DummyDriver < DB::Driver
       return n
     end
 
-    def read?(t : Nil.class)
-      read?.as(Nil)
+    def read(t : String.class)
+      read.to_s
     end
 
-    def read?(t : String.class)
-      read?.try &.to_s
+    def read(t : String?.class)
+      read.try &.to_s
     end
 
-    def read?(t : Int32.class)
-      read?(String).try &.to_i32
+    def read(t : Int32.class)
+      read(String).to_i32
     end
 
-    def read?(t : Int64.class)
-      read?(String).try &.to_i64
+    def read(t : Int64.class)
+      read(String).to_i64
     end
 
-    def read?(t : Float32.class)
-      read?(String).try &.to_f32
+    def read(t : Float32.class)
+      read(String).to_f32
     end
 
-    def read?(t : Float64.class)
-      read?(String).try &.to_f64
+    def read(t : Float64.class)
+      read(String).to_f64
     end
 
-    def read?(t : Bytes.class)
-      value = read?
-      if value.is_a?(Nil)
-        value
-      elsif value.is_a?(String)
+    def read(t : Bytes.class)
+      case value = read
+      when String
         ary = value.bytes
         Slice.new(ary.to_unsafe, ary.size)
-      elsif value.is_a?(Bytes)
+      when Bytes
         value
       else
         raise "#{value} is not convertible to Bytes"

spec/dummy_driver_spec.cr

@@ -74,11 +74,11 @@ describe DummyDriver do
       with_dummy do |db|
         db.query "a,NULL 1,NULL" do |rs|
           rs.move_next
-          rs.read?(String).should eq("a")
-          rs.read?(String).should be_nil
+          rs.read(String).should eq("a")
+          rs.read(String | Nil).should be_nil
           rs.move_next
-          rs.read?(Int64).should eq(1)
-          rs.read?(Int64).should be_nil
+          rs.read(Int64).should eq(1)
+          rs.read(Int64 | Nil).should be_nil
         end
       end
     end
@@ -96,6 +96,116 @@ describe DummyDriver do
       end
     end
 
+    describe "query one" do
+      it "queries" do
+        with_dummy do |db|
+          db.query_one("3,4", &.read(Int64, Int64)).should eq({3i64, 4i64})
+        end
+      end
+
+      it "raises if more than one row" do
+        with_dummy do |db|
+          expect_raises(DB::Error, "more than one row") do
+            db.query_one("3,4 5,6") { }
+          end
+        end
+      end
+
+      it "raises if no rows" do
+        with_dummy do |db|
+          expect_raises(DB::Error, "no rows") do
+            db.query_one("") { }
+          end
+        end
+      end
+
+      it "with as" do
+        with_dummy do |db|
+          db.query_one("3,4", as: {Int64, Int64}).should eq({3i64, 4i64})
+        end
+      end
+
+      it "with as, just one" do
+        with_dummy do |db|
+          db.query_one("3", as: Int64).should eq(3i64)
+        end
+      end
+    end
+
+    describe "query one?" do
+      it "queries" do
+        with_dummy do |db|
+          value = db.query_one?("3,4", &.read(Int64, Int64))
+          value.should eq({3i64, 4i64})
+          value.should be_a(Tuple(Int64, Int64)?)
+        end
+      end
+
+      it "raises if more than one row" do
+        with_dummy do |db|
+          expect_raises(DB::Error, "more than one row") do
+            db.query_one?("3,4 5,6") { }
+          end
+        end
+      end
+
+      it "returns nil if no rows" do
+        with_dummy do |db|
+          db.query_one?("") { fail("block shouldn't be invoked") }.should be_nil
+        end
+      end
+
+      it "with as" do
+        with_dummy do |db|
+          value = db.query_one?("3,4", as: {Int64, Int64})
+          value.should be_a(Tuple(Int64, Int64)?)
+          value.should eq({3i64, 4i64})
+        end
+      end
+
+      it "with as, just one" do
+        with_dummy do |db|
+          value = db.query_one?("3", as: Int64)
+          value.should be_a(Int64?)
+          value.should eq(3i64)
+        end
+      end
+    end
+
+    describe "query all" do
+      it "queries" do
+        with_dummy do |db|
+          ary = db.query_all "3,4 1,2", &.read(Int64, Int64)
+          ary.should eq([{3, 4}, {1, 2}])
+        end
+      end
+
+      it "queries with as" do
+        with_dummy do |db|
+          ary = db.query_all "3,4 1,2", as: {Int64, Int64}
+          ary.should eq([{3, 4}, {1, 2}])
+        end
+      end
+
+      it "queries with as, just one" do
+        with_dummy do |db|
+          ary = db.query_all "3 1", as: Int64
+          ary.should eq([3, 1])
+        end
+      end
+    end
+
+    it "reads multiple values" do
+      with_dummy do |db|
+        db.query "3,4 1,2" do |rs|
+          rs.move_next
+          rs.read(Int64, Int64).should eq({3i64, 4i64})
+          rs.move_next
+          rs.read(Int64, Int64).should eq({1i64, 2i64})
+        end
+      end
+    end
+
     it "should enumerate blob fields" do
       with_dummy do |db|
         db.query("az,AZ") do |rs|
@@ -110,22 +220,13 @@ describe DummyDriver do
 
     it "should get Nil scalars" do
       with_dummy do |db|
-        DummyDriver::DummyResultSet.next_column_type = Nil
         db.scalar("NULL").should be_nil
       end
     end
 
     {% for value in [1, 1_i64, "hello", 1.5, 1.5_f32] %}
-      it "numeric scalars of type of {{value.id}} should return value or nil" do
-        with_dummy do |db|
-          DummyDriver::DummyResultSet.next_column_type = typeof({{value}})
-          db.scalar("#{{{value}}}").should eq({{value}})
-        end
-      end
-
       it "should set positional arguments for {{value.id}}" do
         with_dummy do |db|
-          DummyDriver::DummyResultSet.next_column_type = typeof({{value}})
           db.scalar("?", {{value}}).should eq({{value}})
         end
       end
@@ -135,7 +236,6 @@ describe DummyDriver do
       with_dummy do |db|
         ary = UInt8[0x53, 0x51, 0x4C]
         slice = Bytes.new(ary.to_unsafe, ary.size)
-        DummyDriver::DummyResultSet.next_column_type = typeof(slice)
         (db.scalar("?", slice).as(Bytes)).to_a.should eq(ary)
       end
     end

src/db.cr

@@ -126,3 +126,4 @@ require "./db/driver"
 require "./db/connection"
 require "./db/statement"
 require "./db/result_set"
+require "./db/error"

src/db/error.cr

@@ -0,0 +1,4 @@
+module DB
+  class Error < Exception
+  end
+end

src/db/query_methods.cr

@@ -21,27 +21,190 @@ module DB
     # :nodoc:
     abstract def prepare(query) : Statement
 
-    # Returns a `ResultSet` for the `query`.
+    # Executes a *query* and returns a `ResultSet` with the results.
     # The `ResultSet` must be closed manually.
+    #
+    # ```
+    # result = db.query "select name from contacts where id = ?", 10
+    # begin
+    #   if result.move_next
+    #     id = result.read(Int32)
+    #   end
+    # ensure
+    #   result.close
+    # end
+    # ```
     def query(query, *args)
       prepare query, &.query(*args)
     end
 
-    # Yields a `ResultSet` for the `query`.
+    # Executes a *query* and yields a `ResultSet` with the results.
     # The `ResultSet` is closed automatically.
+    #
+    # ```
+    # db.query("select name from contacts where age > ?", 18) do |rs|
+    #   rs.each do
+    #     name = rs.read(String)
+    #   end
+    # end
+    # ```
     def query(query, *args)
       # CHECK prepare(query).query(*args, &block)
       rs = query(query, *args)
       yield rs ensure rs.close
     end
 
+    # Executes a *query* that expects a single row and yields a `ResultSet`
+    # positioned at that first row.
+    #
+    # The given block must not invoke `move_next` on the yielded result set.
+    #
+    # Raises `DB::Error` if there were no rows, or if there were more than one row.
+    #
+    # ```
+    # name = db.query_one "select name from contacts where id = ?", 18, &.read(String)
+    # ```
+    def query_one(query, *args, &block : ResultSet -> U) : U
+      query(query, *args) do |rs|
+        raise DB::Error.new("no rows") unless rs.move_next
+
+        value = yield rs
+        raise DB::Error.new("more than one row") if rs.move_next
+        return value
+      end
+    end
+
+    # Executes a *query* that expects a single row and returns it
+    # as a tuple of the given *types*.
+    #
+    # Raises `DB::Error` if there were no rows, or if there were more than one row.
+    #
+    # ```
+    # db.query_one "select name, age from contacts where id = ?", 1, as: {String, Int32}
+    # ```
+    def query_one(query, *args, as types : Tuple)
+      query_one(query, *args) do |rs|
+        rs.read(*types)
+      end
+    end
+
+    # Executes a *query* that expects a single row
+    # and returns the first column's value as the given *type*.
+    #
+    # Raises `DB::Error` if there were no rows, or if there were more than one row.
+    #
+    # ```
+    # db.query_one "select name from contacts where id = ?", 1, as: String
+    # ```
+    def query_one(query, *args, as type : Class)
+      query_one(query, *args) do |rs|
+        rs.read(type)
+      end
+    end
+
+    # Executes a *query* that expects at most a single row and yields a `ResultSet`
+    # positioned at that first row.
+    #
+    # Returns `nil`, not invoking the block, if there were no rows.
+    #
+    # Raises `DB::Error` if there were more than one row
+    # (this ends up invoking the block once).
+    #
+    # ```
+    # name = db.query_one? "select name from contacts where id = ?", 18, &.read(String)
+    # typeof(name) # => String | Nil
+    # ```
+    def query_one?(query, *args, &block : ResultSet -> U) : U?
+      query(query, *args) do |rs|
+        return nil unless rs.move_next
+
+        value = yield rs
+        raise DB::Error.new("more than one row") if rs.move_next
+        return value
+      end
+    end
+
+    # Executes a *query* that expects a single row and returns it
+    # as a tuple of the given *types*.
+    #
+    # Returns `nil` if there were no rows.
+    #
+    # Raises `DB::Error` if there were more than one row.
+    #
+    # ```
+    # result = db.query_one? "select name, age from contacts where id = ?", 1, as: {String, Int32}
+    # typeof(result) # => Tuple(String, Int32) | Nil
+    # ```
+    def query_one?(query, *args, as types : Tuple)
+      query_one?(query, *args) do |rs|
+        rs.read(*types)
+      end
+    end
+
+    # Executes a *query* that expects a single row
+    # and returns the first column's value as the given *type*.
+    #
+    # Returns `nil` if there were no rows.
+    #
+    # Raises `DB::Error` if there were more than one row.
+    #
+    # ```
+    # name = db.query_one? "select name from contacts where id = ?", 1, as: String
+    # typeof(name) # => String?
+    # ```
+    def query_one?(query, *args, as type : Class)
+      query_one?(query, *args) do |rs|
+        rs.read(type)
+      end
+    end
+
+    # Executes a *query* and yield a `ResultSet` positioned at the beginning
+    # of each row, returning an array of the values of the blocks.
+    #
+    # ```
+    # names = db.query_all "select name from contacts", &.read(String)
+    # ```
+    def query_all(query, *args, &block : ResultSet -> U) : Array(U)
+      ary = [] of U
+      query(query, *args) do |rs|
+        rs.each do
+          ary.push(yield rs)
+        end
+      end
+      ary
+    end
+
+    # Executes a *query* and returns an array where each row is
+    # read as a tuple of the given *types*.
+    #
+    # ```
+    # contacts = db.query_all "select name, age from contactas", as: {String, Int32}
+    # ```
+    def query_all(query, *args, as types : Tuple)
+      query_all(query, *args) do |rs|
+        rs.read(*types)
+      end
+    end
+
+    # Executes a *query* and returns an array where there first
+    # column's value of each row is read as the given *type*.
+    #
+    # ```
+    # names = db.query_all "select name from contactas", as: String
+    # ```
+    def query_all(query, *args, as type : Class)
+      query_all(query, *args) do |rs|
+        rs.read(type)
+      end
+    end
+
     # Performs the `query` and returns an `ExecResult`
     def exec(query, *args)
       prepare query, &.exec(*args)
     end
 
-    # Performs the `query` and returns a single scalar `DB::Any` value
-    # puts db.scalar("SELECT MAX(name)") as String # => (a String)
+    # Performs the `query` and returns a single scalar value
+    # puts db.scalar("SELECT MAX(name)").as(String) # => (a String)
     def scalar(query, *args)
       prepare query, &.scalar(*args)
     end
@@ -55,7 +218,5 @@ module DB
         raise ex
       end
     end
-
-    # TODO add query_row
   end
 end

src/db/result_set.cr

@@ -16,10 +16,9 @@ module DB
   # ### Note to implementors
   #
   # 1. Override `#move_next` to move to the next row.
-  # 2. Override `#read?(t)` for all `t` in `DB::TYPES` and any other types the driver should handle.
-  # 3. (Optional) Override `#read(t)` for all `t` in `DB::TYPES` and any other.
+  # 2. Override `#read` returning the next value in the row.
+  # 3. (Optional) Override `#read(t)` for some types `t` for which custom logic other than a simple cast is needed.
   # 4. Override `#column_count`, `#column_name`.
-  # 5. Override `#column_type`. It must return a type in `DB::TYPES`.
   abstract class ResultSet
     include Disposable
 
@@ -55,30 +54,29 @@ module DB
     # Returns the name of the column in `index` 0-based position.
     abstract def column_name(index : Int32) : String
 
-    # Returns the type of the column in `index` 0-based position.
-    # The result is one of `DB::TYPES`.
-    abstract def column_type(index : Int32)
+    # Reads the next column value
+    abstract def read
 
-    def read(t)
-      read?(t).not_nil!
+    # Reads the next column value as a **type**
+    def read(type : T.class) : T
+      read.as(T)
     end
 
-    # Reads the next column as a Nil.
-    def read(t : Nil.class) : Nil
-      read?(Nil)
+    # Reads the next columns and returns a tuple of the values.
+    def read(*types : Class)
+      internal_read(*types)
     end
 
-    def read?(t)
-      raise "read?(t : #{t}) is not implemented in #{self.class}"
+    private def internal_read(*types : *T)
+      {% begin %}
+        Tuple.new(
+          {% for type in T %}
+            read({{type.instance}}),
+          {% end %}
+        )
+      {% end %}
     end
 
-    # list datatypes that must be supported form the driver
-    # users will call read(String) or read?(String) for nillables
-    {% for t in DB::TYPES %}
-      # Reads the next column as a nillable {{t}}.
-      abstract def read?(t : {{t}}.class) : {{t}}?
-    {% end %}
-
     # def read_blob
     #   yield ... io ....
     # end

src/db/statement.cr

@@ -45,7 +45,7 @@ module DB
     def scalar(*args)
       query(*args) do |rs|
         rs.each do
-          return rs.read?(rs.column_type(0))
+          return rs.read
         end
       end