Add `get_pulse` and `get_gradient`

src/containers/abstract.jl

 module Abstract
-import ...Variables: AbstractBlock, duration, effective_time, gradient_strength, amplitude, phase, VariableType
+import ...Variables: AbstractBlock, duration, effective_time, gradient_strength, amplitude, phase, VariableType, get_pulse, get_gradient
 import ...Components.Readouts: readout_times
-import ...Components: BaseComponent, InstantPulse, InstantGradient, ReadoutComponent
+import ...Components: BaseComponent, InstantPulse, InstantGradient, ReadoutComponent, NoGradient, RFPulseComponent, GradientWaveform
 
 """
 Parent type for `BuildingBlock` or `BaseSequence`, i.e., any building block that contains other MRI components/blocks.
@@ -120,6 +120,29 @@ Returns all the [`InstantGradient`](@ref) within the sequence with their timings
 iter_instant_gradients(container::ContainerBlock) = iter(container, Val(:instantgradient))
 iter(component::Tuple{<:Number, <:InstantGradient}, ::Val{:instantgradient}) = [component]
 
+"""
+    get_pulse(container, time)
+
+Gets the pulse running at a particular `time` (in ms) during a sequence of building block.
+
+If there is a RF pulse, this function will return a tuple with 2 elements:
+1. The [`RFPulseComponent`](@ref) itself
+2. The time since the start of the pulse
+If there is no active RF pulse, `nothing` is returned.
+"""
+function get_pulse end
+
+"""
+    get_gradient(container, time)
+
+Gets the gradient running at a particular `time` (in ms) during a sequence of building block.
+
+This function will return a tuple with 2 elements:
+1. The [`GradientWaveform`](@ref) itself (which could be a [`NoGradient`](@ref) object).
+2. The time since the start of the gradient
+"""
+function get_gradient end
+
 """
     readout_times(sequence)
 

src/containers/base_sequences.jl

@@ -4,7 +4,7 @@ Defines [`BaseSequence`](@ref) and [`Sequence`](@ref)
 module BaseSequences
 import StaticArrays: SVector
 import JuMP: @constraint
-import ...Variables: get_free_variable, repetition_time, VariableType, duration, variables, VariableNotAvailable, Variables, set_simple_constraints!, TR, make_generic, gradient_strength, amplitude, phase, gradient_strength3
+import ...Variables: get_free_variable, repetition_time, VariableType, duration, variables, VariableNotAvailable, Variables, set_simple_constraints!, TR, make_generic, gradient_strength, amplitude, phase, gradient_strength3, get_gradient, get_pulse
 import ...BuildSequences: global_model, global_scanner
 import ...Components: EventComponent, NoGradient
 import ...Scanners: Scanner, B0
@@ -114,7 +114,7 @@ function edge_times(seq::BaseSequence; tol=1e-6)
     return sort(unique_res)
 end
 
-for fn in (:gradient_strength, :amplitude, :phase, :gradient_strength3)
+for fn in (:gradient_strength, :amplitude, :phase, :gradient_strength3, :get_gradient, :get_pulse)
     @eval function $fn(sequence::BaseSequence, time::AbstractFloat)
         (block_time, block) = sequence(time)
         return $fn(block, block_time)

src/containers/building_blocks.jl

@@ -9,7 +9,7 @@ import ..Abstract: ContainerBlock, start_time, readout_times, edge_times, end_ti
 import ...BuildSequences: global_model
 import ...Components: BaseComponent, GradientWaveform, EventComponent, NoGradient, ChangingGradient, ConstantGradient, split_gradient, RFPulseComponent, ReadoutComponent, InstantGradient
 import ...Variables: qval, bmat_gradient, effective_time, get_free_variable, qval3, slew_rate, gradient_strength, amplitude, phase
-import ...Variables: VariableType, duration, make_generic, get_pulse, get_readout, scanner_constraints!
+import ...Variables: VariableType, duration, make_generic, get_pulse, get_readout, scanner_constraints!, get_gradient
 
 """
 Basic BuildingBlock, which can consist of a gradient waveforms with any number of RF pulses/readouts overlaid
@@ -221,24 +221,38 @@ function edge_times(bb::BaseBuildingBlock)
     return sort(unique(res))
 end
 
+function get_pulse(bb::BaseBuildingBlock, time::Number)
+    for (key, component) in events(bb)
+        if component isa RFPulseComponent && (start_time(bb, key) <= time <= end_time(bb, key))
+            return (component, time - start_time(bb, key))
+        end
+    end
+    return nothing
+end
+
 for (fn, default_value) in ((:amplitude, 0.), (:phase, NaN))
     @eval function $fn(bb::BaseBuildingBlock, time::Number)
-        for (key, block) in events(bb)
-            if block isa RFPulseComponent && start_time(bb, key) <= time <= end_time(bb, key)
-                return $fn(block, time - start_time(bb, key))
-            end
+        pulse = get_pulse(bb, time)
+        if isnothing(pulse)
+            return $default_value
         end
-        return $default_value
+        return $fn(pulse[1], pulse[2])
     end
 end
 
-function gradient_strength(bb::BaseBuildingBlock, time::Number)
+
+function get_gradient(bb::BaseBuildingBlock, time::Number)
     for (key, block) in waveform_sequence(bb)
         if (start_time(bb, key) <= time <= end_time(bb, key)) || (time ≈ end_time(bb, key))
-            return gradient_strength(block, time - start_time(bb, key))
+            return (block, time - start_time(bb, key))
         end
     end
-    error("$bb with duration $(duration(bb)) does not define a gradient strength at time $time.")
+    error("$bb with duration $(duration(bb)) does not define a gradient at time $time.")
+end
+
+function gradient_strength(bb::BaseBuildingBlock, time::Number)
+    (grad, time) = get_gradient(bb, time)
+    return gradient_strength(grad, time)
 end
 
 """

test/runtests.jl

@@ -2,7 +2,7 @@ using MRIBuilder
 using Test
 
 @testset "MRIBuilder.jl" begin
-    #include("test_sequences.jl")
-    #include("test_IO.jl")
+    include("test_sequences.jl")
+    include("test_IO.jl")
     include("test_plot.jl")
 end

test/test_sequences.jl

@@ -88,6 +88,17 @@
                 @test length(readout_times(seq)) > 50
                 @test 67 < TE(seq) < 68
                 @test 72 < TR(seq) < 73
+
+                (pulse, t_pulse) = get_pulse(seq, 1.)
+                @test 1. - t_pulse ≈ min_rise_time rtol=1e-4
+                @test flip_angle(pulse) ≈ 90.
+                @test iszero(phase(pulse))
+                @test isnothing(get_pulse(seq, 10.))
+
+                (pulse, t_pulse) = get_pulse(seq, 35.)
+                @test 1.1 < t_pulse < 1.2
+                @test flip_angle(pulse) ≈ 180.
+                @test iszero(phase(pulse))
             end
         end